Added draggable and dragging CSS styles for the spec suite.
Defaults now get applied to configuration passed in through $.draggable(). Renamed the draggable/dragging class options to draggableClass and draggingClass.
We now apply 'position' and the dragging class to the draggable only when we consider the drag to have started.
No need to store a reference to the document in every draggable.
Reorganized the specs, moving generally applicable specificatinos into an 'any draggable' section.
Added isNumber() and isNaN() to the spec helpers.
Consider the original top and left when testing whether a draggable moved.
Updated the banner section in draggable.coffee.