Replace load-in of YAML data with Jekyll::Document logic.

COLLECTIONS IS COMING
OMG it's happening ~*Collections*~
Hey girl, i heard you like YAML.
DEM TESTS
Sort the docs based on path
Expect site.data stuff to be hashes
GUYS failing test for rendering
Strike duplicate methods & :collection_name filler
OMG COLLECTIONS ARE RENDERING CALL THE POLICE
Don't let that render get you down.
Homagah it all renders I think.
Add some documentation
I am the King of Copy
Add docs for how the collections stuff is exposed via Liquid.
SANITIZE THE collection name plz.
Moar tests for collections.
Add comments for Collection
Do not render any asset files with Liquid.
Add comments for Document
Expose collections as site.<collection_name> in Liquid as array of docs.