Build system refactor

This upgrades the current build system to Grunt .4 (being released tomorrow) and converts the Gruntfile to CoffeeScript. Adds Uglify for minification and CSS minification. Much cleaner build/dist directory, and less repetitive tasks. Also adds a `watch` command (with LiveReload enabled).

The only really subjective part of this PR is that I've pulled out all hard-copied source files from the repo, meaning demos will no longer work directly after checking out the repo (must be built first). Let me know if there are objections, but this is a much cleaner way to maintain the source. Full built files will still be available in the download/release of course.