Add CI for Go 1.4

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index f825220..9398694 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,4 +7,5 @@
   - 1.1
   - 1.2
   - 1.3
+  - 1.4
   - tip