Send the correct element for fragmenthidden events

Specify position for .reveal.linear sections. fixes #64

Changed #reveal to .reveal in print.css

fix JS error when controls are removed from HTML 

Expose navigatePrev, navigateNext

no need to include the controls in html

simplified handling of nested lists

Added overview toggle to allow for button-based overview toggling

Added add/removeEvents methods to allow for adding& removing event
listeners that may interfere with other libs.

added left, right, up, down gestures to change slides. moved window edge slide triggers to a touchend event to prevent interference of gestures