note the forked source in readme

Author: kurttheviking

README.md

@@ -1,7 +1,7 @@
 git-rev-sync
 ============
 
-Synchronously get the current git commit hash, tag, or branch
+Synchronously get the current git commit hash, tag, or branch. Forked from [git-rev](https://github.com/tblobaum/git-rev).
 
 
 ## Example