Don't run tests against ancient versions on Travis (#438)

Don't run tests against ancient versions on Travis.

.travis.yml

@@ -1,26 +1,13 @@
 sudo: false
 language: go
 go:
-  - 1.5.4
-  - 1.6.2
+  - "1.9.x"
+  - "1.10.x"
   - tip
 matrix:
-  include:
-    - go: 1.2.2
-      script:
-        - go get -t -v ./...
-        - go test -v -race ./...
-    - go: 1.3.3
-      script:
-        - go get -t -v ./...
-        - go test -v -race ./...
-    - go: 1.4.3
-      script:
-        - go get -t -v ./...
-        - go test -v -race ./...
+  fast_finish: true
   allow_failures:
     - go: tip
-  fast_finish: true
 install:
   - # Do nothing. This is needed to prevent default install action "go get -t -v ./..." from happening here (we want it to happen inside script step).
 script: