added some failing tests for the Yoda fixer

Then it is not a metter of fixing a bug but changing the idea behind Yoda fixer.
It assumes that variable should be on right, and on left should be constant/literal/expresion,not only constant.
Please take a look at more cases that are fixed by Yoda fixer: https://github.com/FriendsOfPHP/PHP-CS-Fixer/blob/master/Symfony/CS/Tests/Fixer/Symfony/YodaConditionsFixerTest.php#L46

Btw when looking for a taste I dislike yoda conditions itself. I just can't misspelled `===` with `=` (triple with single). But that's only my deviation I guess ;)