Simplify API access with an api.js file

[alexander-bauer]

This should be a simple wrapper to the NodeAtlas API endpoints in whatever way makes most sense, so that other webpages could embed functions tied to particular NodeAtlas instances.

[lukevers]

If I'm correct in understanding what you're suggesting, it's that we have a file called api.js that users can put on their own sites, and use functions from that file to get information from our map(s)?