add versions table, and model
add versionable concern, allow a user to edit an anime entry (certain fields)
create index page of pending edits
add link to pending page to kotodama
add pending.show page
implement approve/reject of edits
limit pending page to staff only
use psql 9.3 for json data type on travis
add controller tests
add model test, add test for creating an edit
renamed 'pending' route to 'edits', fixups based on @vikhyat's feedback
Merge pull request #296 from vevix/wikify-1

[WIP] Wiki Part 1!