add $message everywhere

[pretzlaw]

Usually assertions to allow to override the exception message:

public static function assertEquals($expected, $actual, $message = '', $delta = 0.0, $maxDepth = 10, $canonicalize = false, $ignoreCase = false)

Unfortunately our signature do not allow this

public static function assertFilterHasCallback($filter, $expectedCallback)

So we add a third argument to all tests forwarding the message to static::assertThat.

• Depends on use assertThat everywhere #2