Removed DoubleTapZoom parameter startZoom, since it's always normalizedScale
Added getMaxZoom, getMinZoom, and getCurrentZoom to public API.
Bug fix: setImage causes image to disappear

https://github.com/MikeOrtiz/TouchImageView/issues/41
Merge branch 'setImage' into dev
maintainZoomAfterSetImage added to public API.
Updated README to include maintainZoomAfterSetImage
Bug fix for crash when no image has been set.
Merge branch 'maintainZoom' into dev
Updated public API and README to clarify that default value for maintainZoomAfterSetImage is true.
Merge branch 'dev'