Revert incompatible changes


git-svn-id: svn://svn.twistedmatrix.com/svn/Twisted/branches/filesender-py3-6026@37085 bbbe8e31-12d6-0310-92fd-ac37d47ddeeb
Use BytesIO instead of file


git-svn-id: svn://svn.twistedmatrix.com/svn/Twisted/branches/filesender-py3-6026@37086 bbbe8e31-12d6-0310-92fd-ac37d47ddeeb
Add a test for multiple chunks


git-svn-id: svn://svn.twistedmatrix.com/svn/Twisted/branches/filesender-py3-6026@37087 bbbe8e31-12d6-0310-92fd-ac37d47ddeeb