Handling offset frameRects properly

This fixes an issue I was having where I have a navigation bar above the frameView, which caused the image to be offset from the crop area incorrectly. This is because cropRect is used in view-space in HFImageEditorFrameView, but in screen-space in HFImageEditorViewController.


Commit message:
Making HFImageEditorFrameView store screenspace coordinates for cropRect so that HFImageEditorViewController respects frameView origins other than 0,0

P.S. This library really helped me out. Thanks!