Travis config: add Go 1.10.x, revert 1.4.x to 1.4

1.4.x is missing go vet

.travis.yml

@@ -3,12 +3,13 @@ sudo: false
 
 matrix:
   include:
-    - go: 1.4.x
+    - go: 1.4
     - go: 1.5.x
     - go: 1.6.x
     - go: 1.7.x
     - go: 1.8.x
     - go: 1.9.x
+    - go: 1.10.x
     - go: tip
   allow_failures:
     - go: tip