rest-gen: Add Node.js support

This commit changes the base JavaScript code to work both as a Node.js
module and as a browser script. It should also work as an AMD module.
When running in Node.js, the API will use the `request` package to make
the HTTP requests, instead of jQuery's AJAX functionality.
base.js: Swap callback param order for consistency
Merge pull request #50 from mbrock/master

rest-gen: Add Node.js support