Organize into modules

[letmaik]

I use this library in a browser context and only need a subset of its functionality. It would be great if the different parts of this package are split into separate modules/files (not packages!) such that I can import only certain functionality and have a smaller network footprint. For example, I don't need to run expansion or normalization algorithms and don't need the jquery or node document loaders.

[dlongley]

@neothemachine,

This is being worked on in #126.

[davidlehn]

Some progress has been made in 0.5.x. It's still CJS but headed towards more module setup.

[dlongley]

Closing as a duplicate of #399.