golang version: remove 1.3 support

Remove golang 1.3 from .travis.yml and also mention the support of 1.4+
golang in requirements.

Author: sahildua2305

.travis.yml

@@ -1,7 +1,6 @@
 language: go
 
 go:
-  - 1.3
   - 1.4
   - 1.5
   - 1.6

README.md

@@ -50,7 +50,7 @@ We've used many similar tools in the past, and most of them are either too slow,
 Which brings us to...
 
 ## Requirements
-* Go 1.3+
+* Go 1.4+
 
 Yup, that's it. You can proxy requests to the Go service through Apache/nginx/etc., but that's not required.