Update Travis config to Go 1.5.4 and 1.6.1
diff --git a/.travis.yml b/.travis.yml
index 1c9decd..00fd5dd 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,8 +2,8 @@
 language: go
 
 go:
-  - 1.5.3
-  - 1.6
+  - 1.5.4
+  - 1.6.1
   - tip
 
 matrix: