Several new features

Hi,

I've added some new things:
- tracking setElement calls which enables a jQuery/Zepto plugin to check which View uses given DOM element (finding a parent View is also supported)
- support for tracking objects created with Backbone's extend helper

Other things:
- added some tests and fixed commented ones
- abstracted logging - this will enable users to set a custom logger which eg. stores events or filters them (I plan to use this feature in a browser extension)