add a cucumber feature to test "published" for pages
Add an --unpublished option to render unpublished posts

Fixes #1337, #469.
add the Publisher class to handle publishing logic
Use Publisher instead of Post#published?
Support "published: false" for pages

Fixes 1034.
Add feature for the "--unsupported" flag

Also make step definitions a little more generic.
delete old superfluous tests; extend feature
Merge pull request #1492 from maul-esel/publishing
Update history to reflect merge of #1492 [ci skip]
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.