Large internal refactoring, hopefully code now is more clear,  consistent and understandable.
`this` in any callback will be the same element, on which pickmeup() was called (actually, the same for internal functions).
Current options (for whatever reason) can be accessed as `$('...').data('pickmeup-options')`.
Root pickmeup element (jQuery collection object) can be accessed as `$('...').get(0).pickmeup` or directly `this.pickmeup` if inside callback.
Tiny style fix.