add carthage compatible badge

Sidhant Gandhi · Sidhant Gandhi · commit f9af994adf52 · 2015-06-23T18:19:43.000-07:00
diff --git a/README.md b/README.md
@@ -1,2 +1,4 @@
 # SYNProgressNavigationController
 A UINavigationControllerSubclass with a minimal progress and message label
+
+[![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)
