versioneer interactions with khmer: screed installed as 2.0

[luizirber]

Using eelpond instructions, screed ends up installed as 2.0:

cd ~/
python2.7 -m virtualenv pondenv
source pondenv/bin/activate
cd pondenv
pip install -U setuptools
git clone --branch v2.0 https://github.com/dib-lab/khmer.git
cd khmer
make install

Seems to be related to python-versioneer/python-versioneer#101