WIP Rewrite

Removed PHPUnit_Extensions_Selenium2PageObject_Model and related files
Moved page object classes in examples to sub folder
Rewritten PHPUnit_Extensions_Selenium2PageObject, e.g. removed __call, changed visibility etc.
Rewritten the PageObjec related tests, e.g. used PHPUnit's mocking instead of pseudo mocks
Fixed test coverage reporting
Updated README