add WC.org badge

Author: Granze

README.md

@@ -1,4 +1,5 @@
-[![Build Status](https://travis-ci.org/Granze/flip-clock.svg?branch=master)](https://travis-ci.org/Granze/flip-clock)
+[![Build Status](https://travis-ci.org/Granze/flip-clock.svg?branch=master)](https://travis-ci.org/Granze/flip-clock) [![Published on webcomponents.org](https://img.shields.io/badge/webcomponents.org-published-blue.svg)](https://www.webcomponents.org/element/granze/flip-clock)
+
 
 # <flip-clock>
 
@@ -18,7 +19,7 @@ A flip clock, timer and countdown made with [Polymer](http://polymer-project.org
 ```
 -->
 ```html
-<flip-clock>...</flip-clock>
+<flip-clock></flip-clock>
 ```
 
 ## Installation