RequireJS Support and Misc Improvements

[mjhasbach]

• Use common.js and paintbrush.js from the root of the repo for the demo
  • Less files to maintain
• Added RequireJS support
• The API is now an object of methods
  • Necessary for compatibility with RequireJS. CommonJS support can now also be easily added in the future.
• Removed unused function normalizeMatrix
• Don't automatically process filters on page load
  • That was interfering with RequireJS support. Another possibility is creating an init method on the paintBrush object which calls addLoadEvent and executes paintBrush.processFilters in the callback. In my opinion, the developers who leverage this library should be able to decide when filters are processed.

If you like this PR, I will write some documentation on how to configure PaintbrushJS as a RequireJS package.

[yannicklamprecht]

Love that last point. I hope that I'm now able to update certain DOM-Elements without recoloring the others.