serve: Refactoring and fixes to be able to serve taxonomy pages. * Page sources' `findPagePath` is renamed to `findPageFactory`, so that it also returns source metadata. * Page refs now store possible hits more properly, and use the previous point to also store metadata. As a result, they can also return a proper factory. * Implement `findPageFactory` correctly in all built-in sources. * When the Chef server matches a taxonomy page, get the source metadata from the page ref in order to make a more proper page. * Make the `getRoute(s)` functions explicitely say if they want taxonomy routes or not.

language: python
python:
  - "3.4"
install:
  - "pip install -r requirements.txt"
  - "pip install -r dev-requirements.txt"
script: py.test