Add gitter badge to README.

Author: nlutsenko

README.md

@@ -8,6 +8,8 @@
 [![Dependencies][dependencies-svg]][dependencies-link]
 [![References][references-svg]][references-link]
 
+[![Join Chat][gitter-svg]][gitter-link]
+
 A library that gives you access to the powerful Parse cloud platform from your iOS or OS X app.
 For more information Parse and its features, see [the website][parse.com] and [getting started][docs].
 
@@ -104,3 +106,6 @@ of patent rights can be found in the PATENTS file in the same directory.
 
  [references-svg]: https://www.versioneye.com/objective-c/parse/reference_badge.svg
  [references-link]: https://www.versioneye.com/objective-c/parse/references
+
+ [gitter-svg]: https://img.shields.io/badge/gitter-join%20chat%20%E2%86%92-brightgreen.svg
+ [gitter-link]: https://gitter.im/ParsePlatform/Chat