Add instructions in the README to run tests

[andreagrandi]

It's unclear what should be the minimum setup and how to reproduce it if a developer wants to run the tests locally.

Assuming a developer has just checked out the source code, what are the requirements (applications, libraries and services to be installed) and the db configuration and initialisation that need to be done to be able to run the unit tests locally?

If these instructions could be added to the README it would be really helpful.

[adborden]

Ping, hard to contribute without being able to run tests for development :)