Fixed callback if DialogFragment called from an other Fragment

Good day to you.
 
I have been trying to use your library in my own project.
And I found out that if I start DialogFragment from an Fragment then I don't receive the interface callback there, but I receive it on Activity which has started this Fragment. 
So I decided to add small changes to your library. 

Please, check it, if everything is allright I will be very happy to help you :)
Since we now have proper checks in place, we no longer need to catch the ClassCastException