Psr0Fixer to tokens

I've rewritten the Psr0Fixer to use tokens instead of raw string, and I've added a leading `<?php` to all test-cases to make `token_get_all` work.

There's one test that fails though: the leading namespace test. Is it truly required behaviour for the fixer to remove leading whitespace? (it isn't mentioned in the PSR-0 standard)

This PR implements the last TODO in #489.
Do not add whitespace to token that is not a whitespace!
For case I mentioned Here you create a Token which is `;\n`, what is not a semicolon, not a whitespace, it is sth weird.
And collection with that weird token will go to every fixer run after this one.

Please insert `new Token(array(T_WHITESPACE, "\n"))` instead.