allow morphTo to return many parents instead of just one

What do you think of this ? For me it allowed to retrieve many parents, instead of just one, without breaking the standard way this was working (it used to return only the last fetched element).

I asked some days ago for a way to do this on stackoverflow, detailed description [here](http://stackoverflow.com/questions/26226124/laravel-straight-morphto-relationship).

If you have questions / ideas to improve, shoot !