get rid of mailchimp and migrate to tinyletter (?)

[peterpeterparker]

Feature Description

Mailchimp is way too expensive for hobbyist like us who send one newsletter around every two months. More than 50$ a month for such service is overpriced.

Therefore we should get rid of it.

I would still keep the newsletter feature, I feel like we use it moderately, it is displayed in your services and as long as users can remove themselves easily, it is ok. Therefore I am thinking replacing mailchimp with Tinyletter.