Guessit

This branch use [guessit as filename parser](https://github.com/wackou/guessit). As this library is specialised in parsing, it should be more robust and it's easier to maintain.

All test cases are passing, so it should work in a real world configuration, but i need some alpha users to test this branch before merging this in the trunk.

What remains to be done before merging:

- [x] A ```parsing``` plugin to switch from guessit parser to previous internal parser, or any other custom one.
- [x] Release a new version of guessit, as some bugs were fixed. 
- [x] Make parsing verbose (to debug parsing easily).
- [ ] At least 3 users have tested this branch on their configuration.

Docstring in wrong place