Revert "Revert "Remove branch whitelist for Travis CI""

This reverts commit fabdcc6.

Author: kruton

.travis.yml

@@ -4,12 +4,6 @@ rvm:
 - 2.1
 script: "bundle exec rake test"
 
-# branch whitelist
-branches:
-  only:
-  - gh-pages     # test the gh-pages branch
-  - /pages-(.*)/ # test every branch which starts with "pages-"
-
 env:
   global:
   - NOKOGIRI_USE_SYSTEM_LIBRARIES=true # speeds up installation of html-proofer