Reimplements range slider without jQuery UI

* Slider movement is relative to where the mouse was clicked inside of it
* Slider handles detect beginning and end of range
* Slider handles detect each other
* Slider handles change selected range
* Handles set start and end on model
* Handles move the cursor programatically
* Renames controls to an hbs file
WIP Refactors slider into Slider class

* Class inits with ratio of total time to place sliders
* Moving handles emits an event with new range markers
* Cursor slider refactored into simple <input type="range">
* All corresponding events interface accordingly with instance methods of Slider, or the properties of <input type="range">
* Styles updated for <input type="range">
* nodes() becomes an object that's set in the render callback to avoid the need to run nodes() all the time