Move rwbuf from commons into pants.

commit 39d266964e2ff39ba0ab9f309b920f474fa83954
Author: John Sirois <jsirois@twitter.com>
Date:   Mon May 5 17:08:39 2014 -0600

    Blank out the __init__.py for easy no-shenanigans checkability.

 src/python/pants/rwbuf/__init__.py | 2 --
 1 file changed, 2 deletions(-)

Testing Done:
$ ./build-support/bin/ci.sh

Bugs closed: 102

Reviewed at https://rbcommons.com/s/twitter/r/308/