Merge pull request #111 from bitstadium/fix/add-carthage-button-1

Add carthage button

Author: Benjamin Scholtysik (Reimold)

README.md

@@ -1,5 +1,6 @@
 [![Build Status](https://travis-ci.org/bitstadium/HockeySDK-iOS.svg?branch=develop)](https://travis-ci.org/bitstadium/HockeySDK-Mac)
 [![Version](https://img.shields.io/cocoapods/v/HockeySDK-Mac.svg)](http://cocoadocs.org/docsets/HockeySDK-Mac)
+[![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)
 [![Slack Status](https://slack.hockeyapp.net/badge.svg)](https://slack.hockeyapp.net)