Fix for iOS 9 Banner not taking navigation bars into account properly

[dtrotzjr]

This fix is based in part @Loadex's feature/newTopLayout branch.

This issue appears to be caused by a bug in iOS 9?

The statement realtViewController.topLayoutGuide seems to go away at some point after we set it here. To be clear it is not nil at run time when [... constraintWithItem:realViewController.topLayoutGuide ...] is called however when I bring this up in Reveal App the constraint is labeled as ???.bottom = MBLMessageBannerView:0x... and the First Item is Unknown.

After a few hours banging my head against a wall this was the best I could come up with and it seems to work but I am skeptical as to how robust this really is.

[thibault-carpentier]

Thanks for the pull request. This can be used as a quickfix is someone really need a fast fix. I will take a look this weekend to see how this can be improved.

[dctrotz]

Yes, I agree this is not a proper fix long term, and is more of a quick hack to keep things moving while the proper solution is found.

[williamsjj]

Was a long term fix ever implemented? Also MessageBanner really doesn't like use_frameworks! in CocoaPods.