WIP: Upgrade to Jekyll2

This work in progress pull request aims to take advantage of some of the new features in Jekyll 2. Specifically:

* Create a licenses collection
* Use the "where" filter wherever possible
* Use defaults
* Use automatic coffee script generation
* (move rules to a data file)

## Outstanding issues:

- [ ] `licenses.json` output contains the entire template (https://github.com/jekyll/jekyll/issues/2655)
- [ ] Redirects don't seem to work for collections (https://github.com/jekyll/jekyll-redirect-from/issues/36)
- [ ] Tooltips seem to have broken someplace in the process

/cc @parkr for context on all the issues I opened against Jekyll-core this morning :smile: