Bump version to Python 3.7 (#121)

* bump version

* enable 3.7 in travis

.travis.yml

@@ -1,7 +1,10 @@
 language: python
 
-python:
-  - "3.6"
+matrix:
+  include:
+    - python: 3.7
+      dist: xenial
+      sudo: true
 
 install:
   - pip install --upgrade pip

README.md

@@ -16,10 +16,10 @@ The py-libp2p team consists of:
 
 ## Development
 
-py-libp2p requires Python 3.6 and the best way to guarantee a clean Python 3.6 environment is with [`virtualenv`](https://virtualenv.pypa.io/en/stable/)
+py-libp2p requires Python 3.7 and the best way to guarantee a clean Python 3.7 environment is with [`virtualenv`](https://virtualenv.pypa.io/en/stable/)
 
 ```sh
-virtualenv -p python3.6 venv
+virtualenv -p python3.7 venv
 . venv/bin/activate
 pip3 install -r requirements_dev.txt
 python setup.py develop

requirements_dev.txt

@@ -1,4 +1,4 @@
-pytest>=3.6
+pytest>=3.7
 codecov
 pytest-cov
 pytest-asyncio

setup.py

@@ -5,7 +5,7 @@ classifiers = [
     (
         "Programming Language :: Python :: %s" % version
     )
-    for version in "3.5 3.6".split()
+    for version in ["3.7"]
 ]