Added SwitchCaseFixer - first draft.

This is to fix #776.  Please refer to original PR - https://github.com/fabpot/PHP-CS-Fixer/pull/2 for a bit more details.
Yes, I did.  I thought I could reuse it here but since it's a private function in BracersFixer so I didn't want to touch it.  Should we move it to the parent class and make it protected?