Fixed link tag typo in README.

Author: jogoodma

README.md

@@ -28,7 +28,7 @@ own application build (see usage below).
 
 ````html
 <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
-<link type="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css"></link>
+<link rel="stylesheet" type="text/css" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css"></link>
 ```
 
 ## Usage