update docs on Rugged::Blob#text a little
update docs on Rugged::Blob#text a little

Acidburn0zzz/rugged,tpickett66/rugged,Acidburn0zzz/rugged,saraid/rugged,saraid/rugged,spraints/rugged,spraints/rugged,tpickett66/rugged,libgit2/rugged,tpickett66/rugged,libgit2/rugged,saraid/rugged,libgit2/rugged,Acidburn0zzz/rugged