Add Orientation event and update basic-gestures demo. 

Update shake to use acceleration and accelerationIncludingGravity if rotationRate is present. Also add new build of Event.js and Event.min.js.

Not sure if I made the file structure correct or if this is even need by the main line project, but I wanted to offer you my updates. I made these changes in support of my custom build of fabric.js.

Thanks!