Update README.md

Use svg instead of png to get badges for better image quality.

Author: PeterDaveHello

README.md

@@ -3,8 +3,8 @@ Angular Tree Control
 
 [![npm version](https://badge.fury.io/js/angular-tree-control.svg)](https://badge.fury.io/js/angular-tree-control)
 [![Bower version](https://badge.fury.io/bo/angular-tree-control.svg)](http://badge.fury.io/bo/angular-tree-control)
-[![Build Status](https://travis-ci.org/wix/angular-tree-control.png)](https://travis-ci.org/wix/angular-tree-control)
-[![Coverage Status](https://coveralls.io/repos/wix/angular-tree-control/badge.png)](https://coveralls.io/r/wix/angular-tree-control)
+[![Build Status](https://travis-ci.org/wix/angular-tree-control.svg)](https://travis-ci.org/wix/angular-tree-control)
+[![Coverage Status](https://coveralls.io/repos/wix/angular-tree-control/badge.svg)](https://coveralls.io/r/wix/angular-tree-control)
 
 Pure [AngularJS](http://www.angularjs.org) based tree control component.