Static parser

Adds Parser::parseFile method for simpler DX
Adds Node::filter method to find children of a given type.
Adds PHPUnit coverage for those methods
Coverage reports:
![](https://dl.dropbox.com/s/o6mzy2rm49wvaf8/Screenshot%202014-03-12%2008.52.48.png)
![](https://dl.dropbox.com/s/1ql27qkhsavyaw3/Screenshot%202014-03-12%2008.52.42.png)