Bump tested go versions

and (maybe?) take advantage of support for N.x version syntax

.travis.yml

@@ -7,18 +7,18 @@ cache:
   - node_modules
 
 go:
-- 1.2.2
-- 1.3.3
-- 1.4
-- 1.5.4
-- 1.6.2
+- 1.2.x
+- 1.3.x
+- 1.4.x
+- 1.5.x
+- 1.6.x
 - master
 
 matrix:
   allow_failures:
   - go: master
   include:
-  - go: 1.6.2
+  - go: 1.6.x
     os: osx
 
 before_script: