Add a simple implementation of intrinsicContentsSize

This is useful if using the image views with Auto layout.
Merge pull request #161 from Abizern/intrinsic-content-size

Add a simple implementation of intrinsicContentsSize
Fix import of QuartzCore for case-sensitive disks
Merge pull request #162 from djmadcat/1.x

Fix import of QuartzCore for case-sensitive disks
Correctly copy public headers to SVGKit

This way #import <SVGKit/SVGKit.h> works