zfec-1.5.1 released, fixing tahoe-breaking problem in 1.5.0

[Brian Warner]

.. and of course zfec-1.5.0 had a packaging problem which broke Tahoe.
It turns out that PBR and Versioneer fight over the same hooks,
preventing the sdist tarball from computing its version correctly. "pip
install zfec" wound up with zfec=="0+unknown", which caused Tahoe to bail.

I've just released zfec-1.5.1 to fix this. Sorry for the breakage.

cheers,
 -Brian