Ability to set database password

[sholladay]

This is a feature request to support passing options to RethinkDB from the init() method.

In particular, I want to set RethinkDB's --initial-password option. I imagine doing it like this...

import test from 'ava';
import { init, cleanup } from 'ava-rethinkdb';

const initialData = {};
const option = {
    password : 'abcdefg'
};

test.before(init(initialData, option));
test.after.always(cleanup);

Now, you might ask, why would I want to set a password, since it's just a test?

Well, it would make it much easier to test my app directly, because my app enforces the use of a database password in order to avoid mistakes that could have nasty consequences in production. I don't want to conditionally enforce it based on environment configuration, as that is something very prone to error as well. My preferred solution is to just always have a password. In the tests, the password can be hardcoded and that's fine.

Great project, btw! I hope it will help more people adopt RethinkDB. Now if only I could install the database from npm...