Describe how django-matomo basically works

[Sammeeey]

Make clear in the README:

• How does django-matomo work bascially? What does it do to enable matomo on Django websites?
• Where does it install matomo?

[mikbuch]

I will clarify these things in the README, thank you for your feedback. Meanwhile the answers to these questions can be found here, in the comment to the other issue: #1