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.
> outer-loop
> inner-loop
> `$tokens->ensureWhitespace...`

So, `ensureWhitespace...` may add a new token, then the collection size will change, so your inner-loop iterates backward, but your outer loop iterate forward and then you need to reset `$limit`.
Isn't it possible to change outer-loop to iterate backward and then you won't need to hacky recalc `$limit` ?