Fixed arguments for ArrayUtils::pushAfter() method.
Rewrote ArrayUtils::flatten() method to use an anonymous function.
Some tweaks and fixed to ArrayUtils::merge() and ArrayUtils::mergeDeep() methods.
Tweaks and fixes to ArrayUtils::join() and ::checkValues() methods.
Tweaked ArrayUtils::cleanEmpty() method.
Tweaked arguments for ArrayUtils::toQueryString() method.
Fixed to ArrayUtils::toObject() method.
Fixes to ArrayUtils::fromObject() method.
ArrayUtils::fromObject() using object's toArray() method now moves on silently if the value returned from it isn't an array.
ArrayUtils class is now fully tested.