Add logs about missconfigurations

Currently, if an invalid name is used, the behavior simply skips it silently. This makes it very difficult to spot typos in the config of the behavior. The [filter function](https://github.com/willdurand/TypehintableBehavior/blob/master/src/TypehintableBehavior.php#L103) should have a `else` branch logging a warning.

Btw, even your own testsuite was affected by this. See #6
