Correct issue with pickerFrame returning 0 for width

First off, love this library. 

I noticed that when I updated via pods that in BSModalPickerBase.m -> picker -> CGRect pickerFrame that self.bounds.size.width was returning 0 in my current iPad application so the picker view was defaulting to 320 wide.

I made a minor change to [UIApplication sharedApplication].keyWindow.rootViewController.view.bounds.size.width

I did try calling the bounds of the superview but that also returned 0.