Build develop branch on travis too!

.travis.yml

@@ -1,8 +1,9 @@
 language: objective-c
-osx_image: beta-xcode6.3
+osx_image: xcode6.4
 branches:
   only:
     - master
+    - develop
 env:
   - LC_CTYPE=en_US.UTF-8 LANG=en_US.UTF-8
 before_install: