Updated MTStatusBarOverlay with support for UIStatusBarStyleBlackTranslucent (including progress), user interaction in history, the ability to remove items from history, and an example app to demonstrate these new features.

[rileytestut]

Includes the same features from my previous pull request, but this is a modified version of a much more recent commit. Took a long time to finally implement, and I suggest you do some more compatibility testing. I've tested it using the example app and everything works fine, but as there a lot of changes you can never be too careful.

Hopefully you and everyone else finds this useful :)

[myell0w]

Wow, thank you for your work and the amount of changes. I did at quick test and it looks very good overall, but I found a few bugs, so I'm afraid it will take me quite some time to do a detailed review and merge this in (probably partly), but I will do - hopefully soon! I can see what you're trying to achieve with the parameter "key", but I don't like that it complicates the API so I think I won't merge this part, but rather use the message itself as the key. That's not 100 % unique and there might be situations where this is a problem, but I still prefer it over the complicated API. Maybe I will find an elegant way to offer at least a solution to specify a custom key.