Created npm package

I pulled out the tileify logic into it's own package. Once you've merged you'll be able to do the following to publish:

1. `npm adduser`
2. `npm publish`

I also put the proxy logic into it's own directory.

Lastly, the only other feature I added was the ability to modify the `url_parameters` for the AGS url, as well as the ability to specify additional query parameters.