v0.2.0

Change Log:

1. Local uploaded JPEG image with EXIF orientation is now shown correctly. Initial image should provide data-exif-orientation attribute to work.
2. canvas-color default value changed from '#e6e6e6' to 'transparent'.
3. New methods to support rotate image: rotate(), flipX(), flipY().
4. New prop disabled-rotation.
5. New prop initial-size to specify image's size when it is first loaded on croppa. It can be 'cover', 'contain' or 'natural'.
6. New prop initial-position to specify image's position relative to croppa container when it is first loaded. It works similar to css's background-position.
7. generateDataUrl() method now accept a second argument to specify the compression rate.
8. New event new-image emitted when new valid image is set onto croppa.
9. Bug fixes.