Implements event direction.
Implements event direction.

Events can have one of two directions passed to them -- forward or reverse.
This depends on whether or not the "new" slide number is higher or lower
than the old one. Using these, reversible events can be implemented
(see #1).

mikeharris100/deck.events.js,ProgRT/deck.js,alexjobs/deck.js-1,twitwi/deck.js,ProgRT/deck.js,alexjobs/deck.js-1,twitwi/deck.js,ProgRT/deck.js,twitwi/deck.js,alexjobs/deck.js-1