Slider: add options for event callbacks 
Datepicker Tests: Prepare for widget-ization tests.
Tests: Correct all 404 errors in the test suite
Interactions: Update widget defaults to match documented API.
Merge branch 'master' into interactions

Conflicts:
	tests/unit/draggable/draggable_common.js
	ui/jquery.ui.draggable.js
	ui/jquery.ui.droppable.js
	ui/jquery.ui.sortable.js