testing on go latest version.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

.travis.yml

@@ -2,9 +2,9 @@ language: go
 sudo: false
 go:
   - 1.4
-  - 1.5
-  - 1.6
-  - 1.7
+  - 1.5.4
+  - 1.6.4
+  - 1.7.4
   - tip
 
 script: