Use SVG version of travis build status badge [skip ci]

Author: t3chnoboy

README.md

@@ -76,7 +76,7 @@ We encourage you to contribute to Ruby on Rails! Please check out the
 
 ## Code Status
 
-* [![Build Status](https://travis-ci.org/rails/rails.png?branch=master)](https://travis-ci.org/rails/rails)
+* [![Build Status](https://travis-ci.org/rails/rails.svg?branch=master)](https://travis-ci.org/rails/rails)
 
 ## License