Update CONTRIBUTING.md

remove hipchat room reference, add apisupport email reference

Author: alexmac05

CONTRIBUTING.md

@@ -39,4 +39,4 @@ always necessary to create a new issue ticket.
 * [General GitHub documentation](http://help.github.com/)
 * [GitHub pull request documentation](http://help.github.com/send-pull-requests/)
 * [HelloSign API documentation](https://www.hellosign.com/api/documentation)
-* [HelloSign API HipChat room](https://www.hipchat.com/gq4BMFKt1)
+* email apisupport@hellosign.com if you have questions