Merge pull request #80 from vuejs-jp/fix/faq

Fix chat link

Author: yyx990803

source/guide/faq.md

@@ -63,4 +63,5 @@ order: 15
 
 - **I want to help!**
 
-    Great! Read the [contribution guide](https://github.com/yyx990803/vue/blob/master/CONTRIBUTING.md) and join discussions on IRC (#vuejs).
+    Great! Read the [contribution guide](https://github.com/yyx990803/vue/blob/master/CONTRIBUTING.md) and join discussions on <a href="https://gitter.im/yyx990803/vue" target="_blank"><img src="https://badges.gitter.im/Join%20Chat.svg"></a>
+