Bump to golang 1.6.2 on Travis

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index b56c60b..e6e68dc 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,7 @@
 go:
     - 1.4.3
     - 1.5.4
-    - 1.6.1
+    - 1.6.2
     - tip
 before_install:
   - go get github.com/axw/gocov/gocov