1.2.0

Changes

• Reorganized the code into an event dispatcher (BellhopEventDispatcher) and the main class (Bellhop)
• Added some basic functionality tests for Travis
• Added support for NPM using require
• In the parent Bellhop instance, no longer saving a reference to contentWindow, instead using a reference to the iframe, in case the iframe changes src, doesn't break in iOS9
• Fixed a bug when adding multiple events to a single handler, e.g. bellhop.on('start end progress', function(){})