Merge pull request #6 from jamesstonehill/avoid-double-builds

Avoid double Travis builds

Author: jamesstonehill

.travis.yml

@@ -5,6 +5,9 @@ before_install:
   - gem update --system
   - gem install bundler
 cache: bundler
+branches:
+  only:
+    - master
 matrix:
   include:
   - rvm: 2.3.8