Removed api_url, it is determined in __constructor instead.
Tests are working (but not passing yet!).
Added missing NotifyValidate class.
factory() returns a Request object instead.
Redirection calls are static.

Fixed DoReauthorization.
PayPal::factory() returns a Request object.
PayPal is more static and used as a helper on Response objects.
Worked on tests.
Removed flatten, it is not guarantee to produce the right array since PayPal uses different tokens for separator.
Fixed new kohana naming convention.
Added a composer.json.
Update README.md
Update README.md