Made sizeThatFits: and thus sizeToFit work on OLImageView
From UIView's documentation for sizeThatFits: "UIImageView object returns the size of the image it is currently displaying"
Merge pull request #19 from ejensen/sizeThatFits

Made sizeThatFits: & thus sizeToFit work
Fix retain cycle by CADisplayLink retaining target.

- displayLink getter will invalidate the displayLink if there is no superview. It will create one if there is none and is needed.
- The methods `- (void)didMoveToWindow` and `- (void)didMoveToSuperview` ensure displayLink creation and invalidation.
- To avoid invalidation and creation when moving parent views or windows, the methods to invalidate are called in the next cycle.
Merge pull request #21 from ondalabs/fixRetainCycle

Fix retain cycle by CADisplayLink retaining target. (fixes #18)
Section about categories in the README

Closes #13
Only create displayLink if there is an animated image.

Also fixes a crash where `changeKeyframe:` would be called without an animated image.
DRY code
less hardcorded class names.
Merge branch 'DRY-OLImage'
Fix #23
imageWithContentsOfFile & initWithContentsOfFile now respect the @2x scale identifier
Merge pull request #24 from ejensen/retina-suffix

Respect the @2x scale identifier
Merge branch 'master' into optimize-frameInterval