Allow user to choose whether or not the parent view controller should be scaled

[dilizarov]

This is a fantastic library, but for my case, I didn't want the fromVC (Parent View Controller) to scale because it looked awkward given my situation. The following code is completely backwards compatible, so anyone gets these changes won't see their code break.

I contemplated whether I should simply ask the user if they want the parent view controller to be scaled or if I should allow them to pass in a CGFloat which defines the scale (by default, you choose 0.85, but the user would be able to choose 1, 0.90, 0.50, etc.). I decided to go against that because while it is simple to introduce, I'd like to think the library as it stands is pretty awesome :).