Use JQ event if original event does not exist

This commit updates the `touchEnd` and `touchLeave` functions to use
the jQuery event object if no originalEvent property exists.

This makes it possible to trigger the events programatically in browser tests.

A similar change was made to `touchStart` and `touchMove` in 038de2a4eb5dda46f0d8facc052eb910a31ffb93
to resolve issues reported in issue #72.