routing: Fix breakages with routing on some versions of Python. Finally figured what happened with change 6baa94da8b16 (this is a Mercurial hash by the way if you're looking at the Git mirror). Between Python 3.6 and 3.7 there was a change where the percent sign ('%') went from being escaped by `re.escape` to _not_ being escaped. So now we need to use different regex patterns dependin on the Python version, yay.

sudo: false
language: python
python:
  - "3.4"
  - "3.5"
  - "3.6"
install:
  - "python setup.py version -f 2.0"
  - "python setup.py sdist --formats=zip"
  - "pip install dist/PieCrust-2.0.zip"
script:
  - "py.test"