Clearer notes on database setup in README

[allyjweir]

I'm a beginner with postgres and just spent a few hours figuring out that I had to include a database username and password in the connection URL. The confusion mostly came from not using the defualt Django database connection settings layout (separate uesrname, password, server, port fields).

Would it be possible to modify the README with a note about this? While I understand this project is mainly for regular developers to save time, maybe this could save the next noob an evening wasted fighting with postgres.

Happy to make an edit from the beginner perspective in a pull request if it would possibly be accepted.

[allyjweir]

Sorry, seeing this is a duplication of issue #39