Updated dev dep

Continuity of [214](https://github.com/chriso/klein.php/pull/214).

 * Added PHPUnit 4, like I said in [PR 211](https://github.com/chriso/klein.php/pull/211#issuecomment-47757372), there is a problem with your tests that use process isolation, they are not passing neither on my local machine nor or travis.
 * Updated other dev dependencies as there are no need to keep them on old versions, especially considering they're dev dependencies ;-).