removed GHNSData+Base64 and ybase64.c in favor of NSData base64 encoding methods
renamed base64EncodedData to base64EncodedString
deprecated gh_MD5WithEncoder: in favor of gh_MD5Base64
Merge pull request #7 from Yelp/basher_base64

Removed ybase64.c and GHNSData+base64 now that NSData methods are public (also fixes analyzer issue)