Update Viewer.js

The original version did call draw() on a regular basis, but drawImage() always gave out the same image of the stream, that was cached, when page has been loaded. (Browser: Firefox 23.0.1)

I therefore added that.image.src = that.image.src; to force a reload of the image from the stream-URL. Unfortunately that lead to a situation where drawImage() was called before loading has been finished. To make it work for me I needed to wait some time between resetting src and calling drawImage(). I choose half the interval time (I increased to 200), to give the browser maximum margin in both directions. 
If someone has a cleaner solution, like automated wait for the image to load, I would be grateful for any hint!
Update Viewer.js

The initial fix didn't work out (misunderstanding about the inner workings of requestAnimationFrame() and "sleep()" on my side). I now propose a different fix. I added the option "interval" to program an update interval and therefore the load. In addition instead of the initial call to draw, I used setInterval() to program a periodic call to draw. To avoid having always the same picture in the cache, I reset the image.src at the end of the draw function. Therefore the browser has one this.interval to load a new image. For my Mozilla setup this works quite well and stable now. I haven't tested it on Chrome, Safari or MSIE.
Update mjpegcanvas.html

Added the option interval to the example required for my proposed change of Viewer.js.
Merge pull request #23 from wintermuteger/patch-1

Update Viewer.js