refactor: Get the taxonomy support back to a functional state. There's now a taxonomy content source that wraps another normal content source like a blog posts' source. It works in tandem with a taxonomy content pipeline that will do the heavy lifting of figuring out what kind of terms exist and need to be baked.

cov-core==1.15.0
coverage==4.0.3
invoke==0.12.2
mock==1.0.1
pytest==2.8.7
pytest-cov==2.2.1
pytest-mock==0.10.1