Extend README.md

[Ryuno-Ki]

Is your feature request related to a problem? Please describe.
This is a follow-up of #7 (comment)
It shall help contributors and users get up-to-speed with this project.

Describe the solution you'd like
A good README should contain the following items (IMHO)

1. The name of the project (Personally, I put badges behind this line, i.e. build status or code coverage)
2. A sentence of what it does. What problem does it solve? Perhaps at a GIF showing of it
3. A single line of how to get a local installation running (virtualenv + clone + execution)
4. How to execute tests (still missing here, e.g. tox or py.test)
5. How to contribute (with a link to CONTRIBUTING.md)
6. License (with a link to LICENSE.txt)

Describe alternatives you've considered
From experience, I already learned myself how to setup most Python projects. You could make people research on their own.
But they will likely go looking elsewhere for a project instead of investing time …

Additional context
You can read up more on pages like

• feedmereadmes
• awesome-readme
• standard-readme