Use correct branch name

Author: DanielRuf

README.md

@@ -13,7 +13,7 @@
   <br>
   <br>
   <a href="https://travis-ci.com/materializecss/materialize">
-    <img src="https://travis-ci.com/materializecss/materialize.svg?branch=master" alt="Travis CI badge">
+    <img src="https://travis-ci.com/materializecss/materialize.svg?branch=v1-dev" alt="Travis CI badge">
   </a>
   <a href="https://badge.fury.io/js/materialize-css">
     <img src="https://badge.fury.io/js/materialize-css.svg" alt="npm version badge">