A little refactoring of the package

* Moved all comands under Command/ folder
* Moved all installation logic into a single SymfonyPackageInstaller
* Added extractor project as dependency
* Updated README. Every line maximum 80 cols. Simple best practice
* Some architectural refactoring
* Added all php header phpdoc
* Added all method and variable phpdoc
* Added composer.phar into .gitignore file
btw, @fabpot is also against this in his projects (and for the same reason): https://github.com/fabpot/PHP-CS-Fixer/pull/527