.travis.yml: add branches [ci skip]

* .travis.yml (branches): automatically run Travis on branches
  created with `git feature` or `git bug` commands.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54017 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

.travis.yml

@@ -68,6 +68,8 @@ branches:
     - ruby_2_1
     - ruby_2_2
     - ruby_2_3
+    - /^feature\//
+    - /^bug\//
 
 # We want to be notified when something happens.
 notifications: