Add hirb to gemfile.  Also add facts to a user's known-facts the first time a deck is accessed
Allow posting to known facts to update the mastery score when a users answers a question correctly.
Hallelujah. Got the post updating to the correct fact's mastery score.
Got the database updating for each known_fact.
Add algo for calculating rate of memory decay on a given fact.
Setup check due facts button on decks index page
Add redirect after modal login
Setup devise
Add class to decks that haven't been added to a user's library
Rename devise views to partials to use them in the login form modal.