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.
You use 4 assignment for `$whitespace` variable, in each 3 concatenations, and the one thing that is different is number of spaces as suffix.
Use sth like `$whitespaceSuffix = '    ';` and then do the concatenation at calling `$tokens->ensureWhitespaceAtIndex`