README: make a definitive decision on v2 import path

This change makes it clear that the v2 import path
is github.com/russross/blackfriday/v2, and updates
various links accordingly.

See https://github.com/russross/blackfriday/issues/587#issuecomment-703393820 for details.

This change also converges the README for v1 and v2
to be consistent, as they've started to drift apart.
(See PR #675 for the equivalent change to the README
on v2 branch.)

For #587.

GitHub-Pull-Request: #674

README.md

@@ -1,6 +1,6 @@
 Blackfriday
-[![Build Status][BuildSVG]][BuildURL]
+[![Build Status][BuildV2SVG]][BuildV2URL]
-[![Godoc][GodocV2SVG]][GodocV2URL]
+[![PkgGoDev][PkgGoDevV2SVG]][PkgGoDevV2URL]
 ===========
 
 Blackfriday is a [Markdown][1] processor implemented in [Go][2]. It
@@ -18,12 +18,21 @@ It started as a translation from C of [Sundown][3].
 Installation
 ------------
 
-Blackfriday is compatible with any modern Go release. With Go and git installed:
+Blackfriday is compatible with modern Go releases in module mode.
+With Go installed:
 
-    go get -u gopkg.in/russross/blackfriday.v2
+    go get github.com/russross/blackfriday
 
-will download, compile, and install the package into your `$GOPATH` directory
+will resolve and add the package to the current development module,
-hierarchy.
+then build and install it. Alternatively, you can achieve the same
+if you import it in a package:
+
+    import "github.com/russross/blackfriday"
+
+and `go get` without parameters.
+
+Old versions of Go and legacy GOPATH mode might work,
+but no effort is made to keep them working.
 
 
 Versions
@@ -32,13 +41,9 @@ Versions
 Currently maintained and recommended version of Blackfriday is `v2`. It's being
 developed on its own branch: https://github.com/russross/blackfriday/tree/v2 and the
 documentation is available at
-https://godoc.org/gopkg.in/russross/blackfriday.v2.
+https://pkg.go.dev/github.com/russross/blackfriday/v2.
 
-It is `go get`-able via [gopkg.in][6] at `gopkg.in/russross/blackfriday.v2`,
+It is `go get`-able in module mode at `github.com/russross/blackfriday/v2`.
-but we highly recommend using package management tool like [dep][7] or
-[Glide][8] and make use of semantic versioning. With package management you
-should import `github.com/russross/blackfriday` and specify that you're using
-version 2.0.0.
 
 Version 2 offers a number of improvements over v1:
 
@@ -60,22 +65,7 @@ Potential drawbacks:
 
 If you are still interested in the legacy `v1`, you can import it from
 `github.com/russross/blackfriday`. Documentation for the legacy v1 can be found
-here: https://godoc.org/github.com/russross/blackfriday
+here: https://pkg.go.dev/github.com/russross/blackfriday.
-
-### Known issue with `dep`
-
-There is a known problem with using Blackfriday v1 _transitively_ and `dep`.
-Currently `dep` prioritizes semver versions over anything else, and picks the
-latest one, plus it does not apply a `[[constraint]]` specifier to transitively
-pulled in packages. So if you're using something that uses Blackfriday v1, but
-that something does not use `dep` yet, you will get Blackfriday v2 pulled in and
-your first dependency will fail to build.
-
-There are couple of fixes for it, documented here:
-https://github.com/golang/dep/blob/master/docs/FAQ.md#how-do-i-constrain-a-transitive-dependencys-version
-
-Meanwhile, `dep` team is working on a more general solution to the constraints
-on transitive dependencies problem: https://github.com/golang/dep/issues/1124.
 
 
 Usage
@@ -125,7 +115,7 @@ Here's an example of simple usage of Blackfriday together with Bluemonday:
 ```go
 import (
     "github.com/microcosm-cc/bluemonday"
-    "gopkg.in/russross/blackfriday.v2"
+    "github.com/russross/blackfriday"
 )
 
 // ...
@@ -175,12 +165,12 @@ anchors for headings when `EXTENSION_AUTO_HEADER_IDS` is enabled. The
 algorithm has a specification, so that other packages can create
 compatible anchor names and links to those anchors.
 
-The specification is located at https://godoc.org/github.com/russross/blackfriday#hdr-Sanitized_Anchor_Names.
+The specification is located at https://pkg.go.dev/github.com/russross/blackfriday#hdr-Sanitized_Anchor_Names.
 
-[`SanitizedAnchorName`](https://godoc.org/github.com/russross/blackfriday#SanitizedAnchorName) exposes this functionality, and can be used to
+[`SanitizedAnchorName`](https://pkg.go.dev/github.com/russross/blackfriday#SanitizedAnchorName) exposes this functionality, and can be used to
 create compatible links to the anchor names generated by blackfriday.
 This algorithm is also implemented in a small standalone package at
-[`github.com/shurcooL/sanitized_anchor_name`](https://godoc.org/github.com/shurcooL/sanitized_anchor_name). It can be useful for clients
+[`github.com/shurcooL/sanitized_anchor_name`](https://pkg.go.dev/github.com/shurcooL/sanitized_anchor_name). It can be useful for clients
 that want a small package and don't need full functionality of blackfriday.
 
 
@@ -250,7 +240,7 @@ implements the following extensions:
     and supply a language (to make syntax highlighting simple). Just
     mark it like this:
 
-        ``` go
+        ```go
         func getTrue() bool {
             return true
         }
@@ -262,7 +252,7 @@ implements the following extensions:
     To preserve classes of fenced code blocks while using the bluemonday
     HTML sanitizer, use the following policy:
 
-    ``` go
+    ```go
     p := bluemonday.UGCPolicy()
     p.AllowAttrs("class").Matching(regexp.MustCompile("^language-[a-zA-Z0-9]+$")).OnElements("code")
     html := p.SanitizeBytes(unsafe)
@@ -273,7 +263,7 @@ implements the following extensions:
 
         Cat
         : Fluffy animal everyone likes
-        
+
         Internet
         : Vector of transmission for pictures of cats
 
@@ -284,7 +274,7 @@ implements the following extensions:
     end of the document. A footnote looks like this:
 
         This is a footnote.[^1]
-        
+
         [^1]: the footnote text.
 
 *   **Autolinking**. Blackfriday can find URLs that have not been
@@ -321,7 +311,7 @@ Other renderers
 Blackfriday is structured to allow alternative rendering engines. Here
 are a few of note:
 
-*   [github_flavored_markdown](https://godoc.org/github.com/shurcooL/github_flavored_markdown):
+*   [github_flavored_markdown](https://pkg.go.dev/github.com/shurcooL/github_flavored_markdown):
     provides a GitHub Flavored Markdown renderer with fenced code block
     highlighting, clickable heading anchor links.
 
@@ -341,6 +331,10 @@ are a few of note:
     provides a drop-in renderer ready to use with Blackfriday, as well as
     options and means for further customization.
 
+*   [Blackfriday-Confluence](https://github.com/kentaro-m/blackfriday-confluence): provides a [Confluence Wiki Markup](https://confluence.atlassian.com/doc/confluence-wiki-markup-251003035.html) renderer.
+
+*   [Blackfriday-Slack](https://github.com/karriereat/blackfriday-slack): converts markdown to slack message style
+
 
 TODO
 ----
@@ -361,13 +355,10 @@ License
    [1]: https://daringfireball.net/projects/markdown/ "Markdown"
    [2]: https://golang.org/ "Go Language"
    [3]: https://github.com/vmg/sundown "Sundown"
-   [4]: https://godoc.org/gopkg.in/russross/blackfriday.v2#Parse "Parse func"
+   [4]: https://pkg.go.dev/github.com/russross/blackfriday/v2#Parse "Parse func"
    [5]: https://github.com/microcosm-cc/bluemonday "Bluemonday"
-   [6]: https://labix.org/gopkg.in "gopkg.in"
-   [7]: https://github.com/golang/dep/ "dep"
-   [8]: https://github.com/Masterminds/glide "Glide"
 
-   [BuildSVG]: https://travis-ci.org/russross/blackfriday.svg?branch=master
+   [BuildV2SVG]: https://travis-ci.org/russross/blackfriday.svg?branch=v2
-   [BuildURL]: https://travis-ci.org/russross/blackfriday
+   [BuildV2URL]: https://travis-ci.org/russross/blackfriday
-   [GodocV2SVG]: https://godoc.org/gopkg.in/russross/blackfriday.v2?status.svg
+   [PkgGoDevV2SVG]: https://pkg.go.dev/badge/github.com/russross/blackfriday/v2
-   [GodocV2URL]: https://godoc.org/gopkg.in/russross/blackfriday.v2
+   [PkgGoDevV2URL]: https://pkg.go.dev/github.com/russross/blackfriday/v2