Pass degrees from the viewer to the viewport. Fix #305
Merge pull request #336 from avandecreme/minorbugs

Pass degrees from the viewer to the viewport. Fix #305
Changelog for #336
Added rotate right/left buttons to default tools
Fixed code style issue.
Updated images for rotate left/right to better match existing buttons.
Added pre-draw event for tiles to allow applications to alter the image just prior to its rendering. This should enable invert, brightness, contrast, sharpen and other transformations to occur naturally through the 'tile-drawing' event listener.

The listener is given the 'rendered' object which is the pre-drawn image on a canvas context object. By altering the 'rendered' object the listener can alter the display results. Since this event gets fired multiple times for the tile, it is wise for the handler to track what their desired modifications are and to tag the 'tile' element to keep track of the modifications already applied.
Added configuration around the rotate left/right buttons. The default for showRotationControls is false to preserve existing functionality. Also added default tooltip strings for the buttons.

This version runts the tests fine locally using 'npm test'. It looks like the remote build was having a timeout issue which I couldn't reproduce.
Tuned the configuration around the rotate left/right to work when the drawer is instantiated.
Added tests for rotate control on/off setting.
Added test case for tile-drawing event.
Fixed message context to be more correct. I believe the message is only displayed when a failure occurs, so it needs to be clear what was being tested.
Added message to clarify that the event only fires when <canvas> is being used.
Reworded the test messages to 'should be' form as per standard practice.
Added simulated left/right rotate clicks to the test case.
Merge pull request #348 from fs-webdev/tile-drawing-event

Added pre-draw event for tiles to allow applications to alter the image ...
Changelog for #348
Merge pull request #341 from fs-webdev/rotate-buttons

Added Rotate Left/Right buttons to standard controls
Change log for #341
 comment update on rotate test