Use of UIScreen's coordinates

[tooolbox]

Hey there, nice library :)

I was playing around with the video player aspect of it, trying to add AirPlay functionality, and I wanted to warn you that using UIScreen's size/coordinates/etc. (for minimizing & dismissal) is going to backfire if you want to do display mirroring. Maybe better to go off your Key Window?

Anyway, I'm not ending up using MediaView for my project, (the requirements are just too different) but I did run into that issue so I wanted to bring it to your attention. Sorry that I'm not doing a PR :/