Merge pull request rails#147 from dskang/patch-1

Show latest build status for the master branch

Author: rafaelfranca

README.md

@@ -148,7 +148,7 @@ $ bundle install
 $ bundle exec rake test
 ```
 
-[![Build Status](https://secure.travis-ci.org/rails/sprockets-rails.png)](http://travis-ci.org/rails/sprockets-rails)
+[![Build Status](https://travis-ci.org/rails/sprockets-rails.svg?branch=master)](https://travis-ci.org/rails/sprockets-rails)
 
 
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