Make connection an environment variable instead of hard-coded

[OKNoah]

In api/config/databse.js it would be better to have a process.env.MONGO_URL or something rather than a hard-coded connection URL. Then the environment can be passed to the app like env MONGO_URL=mongodb://localhost/test or put in an env file, for example.

[OKNoah]

Also, I feel like it should support full mongo URLs, like mongodb://username:password@server.tld/database. If uploaded to Heroku, for example, the add-ons there will pass this in as an environmental variable in this format. I looked at doing this myself, but I haven't spent enough time with Waterline.