Cakefile to build extensions

[chadselph]

It would be nice to have a Cakefile that could read the manifest.json and build the right zip file for Google Chrome (and possibly other browsers) just based on that. It would have to figure out which things to include dynamically (in addition to adding some manually). It should automatically compile .coffee files to .js before including them in the archive. I may end up just writing this in Python, but if I don't I'll use node-archive.