[#460] Adding dynamic json endpoint.

@jdorfman 

Basically, I'm adding a dynamic endpoint to replace the `wp-plugin.js` script -- although I didn't delete that. This is setup so it only regenerates the JSON on server restart, given that the config is also only updated on server restart, I figured this would be the simplest way. We'll still need to address updating the CDN location (http://maxcdn.bootstrapcdn.com/data/bootstrapcdn.json) in a more automatic way, but this will ensure that http://www.bootstrapcdn.com/data/bootstrapcdn.json is always accurate.

Thoughts?
J