Read credentials from a configuration file.

Hi.
To be more DRY and to enable people to not push their credentials into repositories, I created a simple mechanism to extract credentials from a file.

It's currently only for test purposes but we can extend this, I just need your view on where should I go with this in terms of what configuration files to use and how to store them.

Btw. if you need somebody to collab with on this, I'm willing to participate. There are a few cleanups that can be done here and there (not all tests run properly on my machine for example), and we could discuss some further features.