Merge branch 'master' into interactions

Merge branch 'master' into interactions

Conflicts:
	demos/draggable/constrain-movement.html
	demos/draggable/cursor-style.html
	demos/draggable/default.html
	demos/draggable/events.html
	demos/draggable/handle.html
	demos/draggable/revert.html
	demos/draggable/visual-feedback.html
	demos/droppable/default.html
	grunt.js
	tests/unit/draggable/draggable.html
	tests/unit/draggable/draggable_core.js
	tests/unit/draggable/draggable_options.js
	tests/unit/draggable/draggable_test_helpers.js
	tests/unit/droppable/droppable.html
	tests/unit/droppable/droppable_options.js
	ui/draggable.js
	ui/jquery.ui.droppable.js
	ui/sortable.js