added support for rotating an image by a given number of degrees

setRotationBy(-90) for example, will rotate from the current rotation
-90 degrees, whereas the old method setRotation(-90) would set the
rotation from 0. This is still its the behavior.
deprecated setPhotoViewRotation and added new method setPhotoViewRotationTo
changed names of rotation methods to fit better with the naming convention
Merge pull request #153 from phil-brown/master

Improved Photo Rotation API
Updated build on both Gradle and Travis
Converted Sample to standard sources layout, added AUIL Sample
Changed library project structure and fixed lint warning
Optimized code
Fixed deprecation, using new methods setRotationBy(float) and setRotationTo(float)
Added method IPhotoView getIPhotoViewImplementation(), closing #139
Added setOnDoubleTapListener interface method on IPhotoView with underlying implementation
Fixed Maven configuration to work with latest SDK, project layout and sample dependencies
Fixed inspection issues
Closing #103, Fix problem of scrolling within ViewPager
Lock/Unlock button to temporarily disable ViewPager navigation in order to correctly interact with ImageView by gestures
Merge pull request #167 from juleZZZ/viewpager_lock

Disable ViewPager navigation when interacting with ImageView
merge upstream
merge upstream