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.

sudo: false
language: python
python:
  - "3.4"
  - "3.5"
install:
  - "python setup.py version -f 2.0"
  - "python setup.py sdist --formats=zip"
  - "pip install dist/PieCrust-2.0.zip"
script:
  - "py.test"