Complete rewrite:
    * Widget creation now only in controller
    * Styling now only in TSS
    * Setting message and blocking now only via `show()`
    * Cancel event replaced by callback as second argument for `show()`
    * Second `show()` argument now `cancelable`, *reverse* of `blocking` (!!)
    * On Android, hitting the back button on a non-cancelable loading mask will move app to the background
Merge branch 'master' of https://github.com/FokkeZB/nl.fokkezb.loading

Conflicts:
	README.md