Allow loading in nodejs and browserify.

Hey there! I found your code via a google search, and it looks neat. I'd like to possibly use it in a node or browserify environment, so I added some quick functionality to do so. I did not touch rng.js at all, and simply used some browserify conventions (`browser` field + `browserify-shim` transform) to enable browserify support.

Node support took just using a small wrapper to load `rng.js` and extract the global from it. This could be avoided if `rng.js` had a UMD guard, but I wasn't sure if that would be ok to add.

The only additional work this adds for you, as the package maintainer, is that you keep the version of bower.json and package.json in sync, and publish to each. And of course, if you change something with how `rng.js` exports itself, to run `npm test` to ensure things still pass.

What are your thoughts on this?