Doesn't cover AlertDialog

[danielvandenberg95]

The ShowcaseView is unable to cover up an AlertDialog, and therefore it's not possible to use this on dialogs. This could be solved by expanding the library to also supply the following: http://www.whycouch.com/2013/01/how-to-overlay-view-over-everything-on.html I am not sure if this library is open for a pull-request of this magnitude though. Please let me know if a pull request implementing this feature would be accepted, if so I'll see what I can do.