Add support for CoffeeScript sourceMaps (fixes issue #3)

This patch adds support for CoffeeScript source maps. If `sourceMap` is `true` then the generated source map will be inlined as a data-uri.

I've tested this in Chrome 28 and FireFox 24 – it works fine in the developer console, but unfortunately their JavaScript engines don't use source maps when generating exception stack traces, so it can still take some work to track down the exact line that an exception is failing on.