Reorganized the repo so it's clear what is the library and what is the demo app
Added the default images back
initWithNibName:bundle: calls through to init:. The docs say that if a view is instantiated from a storyboard initWithCoder is called instead. Storyboards have not been tested, this is just going off of what's in the docs.
Removed the protocol. The main view is now always disabled when pushed to the side and objects that want to keep track of the main sliding view can keep a reference to it. Also removed JBMailViewController because a subclass is no longer needed, and UINavigationController is not intended to be subclassed.