Writing readme sections for testing

[Eysteinn-Orn]

Writing the sections in the Readme regarding testing.

Just added some text regarding the testing process, installing dependencies, running tests locally, writing tests, CI, Libraries used, when to test your code and testing guidelines.

[njallskarp]

Approved. Just make one update first. Run the linter and formater (pylint and black) with the fix option to fix some of the 24 issues pointed out by codacy. Once that's good you can merge it

[Eysteinn-Orn]

So, the formatter we are using doesn't format markdown files, what I ended up doing was installing remark using node and running remark . --output using node and that formatted the markdown file as per Codeacy recommendations