PostgreSQL support

[troyjfarrell]

Fixes #65

All changes

• [x] Is this contribution for a known issue in the issues? If so mention it.
• [x] Is there a task for this contribution in the project board? If so mention it.

Code changes

• [x] Have you run the unit tests on the project before submitting the contribution?
• [x] Have you added the appropriate unit tests for your contribution to the project?
• [x] Have you added the appropriate documentation for your contribution to the project?
• [x] Have you styled your code properly based on the contribution guidelines?

Documentation changes

• [x] Have you built the documentation?
• [x] Have you run the documentation tests?