Implementing EventFiringWebDriver and EventFiringWebElement.
Some doc changes and some love for our < php5.4 brothers and sisters.
Unregister key may be 0.
Implemented EventFiringWebDriverNavigation to use the navigation events.
Where applicable, using the underlying element item to find elements.

Abstract class EventFiringObject added to encapsulate some of the generic methods and dispatcher.
Making protected methods into public.

Removed EventFiringObject.
many try/catch statements is a compromise
Licensing and WebDriverEventListener is an interface.

Also simple phpdoc changes for exceptions
Merge remote-tracking branch 'upstream/master'

Conflicts:
	lib/__init__.php
Merge pull request #76 from ashleydw/master

Implement EventFiringWebDriver and EventFiringWebElement