Have all the Mongo ENV variables in one place.

[dblock]

Extract the checking of the ENV variables into a class method and reuse it from the .yml file to avoid repeating the list. It would also let you add a variable without having to update the .yml in all downstream apps.

Related to #31.

[corprew]

@dblock before I commit a fix for this, why is the server checking all the potential mongodb variables rather than having someone set which variable to use in config? I haven't seen that, so figured I'd ask to make sure that I understood your intent.

[dblock]

It's mostly to just be compatible with anything out of the box when deploying to something like Heroku. Less manual labor. If you think there's a better way, happy to hear it!

[dblock]

These are now entirely in mongoid.yml, closing.