The bind() call is deprecated in jQuery 3. This replaces it with
the on() call.

jQuery UI replaced the buttonset widget with a controlgroup widget. This
adjusts the JavaScript and styling accordingly.

If using a west handle, jQuery UI Resizable uses left offset to
position, assuming relative:absolute like setup.

- http://stackoverflow.com/questions/28512111/resizable-div-that-
doesnt-change-left-property
- https://bugs.jqueryui.com/ticket/4985#comment:1

reusing the diff colors as suggested by @selfthinker

missed a line in my last commit

This makes it easier to create tabs with an active tab (no need for
additional markup)

Plugin translation #1

handle 'e' set a resize handle at east side, 'w' at west side.