py-builtins.js should be minified

When generate_library.py is run, the rulting py-builtins.js is a very large file. It would be ideal if generate_library could accept an option to run the output through a javascript minifier of some sort.

For long-term compatibility, this file should also be versioned (probably the same version as pyjaco itself).

Perhaps a little early for this suggestion, but distributing py-builtins.js over a CDN would also make it easier to promote and demo the project.