Fix opaque navbar 2

Second attempt to fix issue #405
I know, it took me a lot of time to figure out this, but looks like ```UIPeriphalHostView``` is rotated when in landscape, when normally the system posts all the ```UIKeyboard```notifications always in window coordinates (not rotated). This was the only way around it. 

This is much like using the X coordinate of the ```touchInWindow``` point when the interface is in landscape ([JSQMessagesKeyboardController.m:332](https://github.com/piercifani/JSQMessagesViewController/blob/fix-opaque-navbar-2/JSQMessagesViewController/Controllers/JSQMessagesKeyboardController.m#L333)).

Anyways, I wanted to find out more about ```UIPeripheralHostView``` but this was the only piece of code that sets it's frame like this. 

If this feels hacky, it's because it probably is. We could use:

``` _scrollView.keyboardDismissMode = UIScrollViewKeyboardDismissModeInteractive;``` 

like [RDRStickyKeyboardView](https://github.com/datwelk/RDRStickyKeyboardView) does