Add a LICENSE

[davidak]

First of all, add a LICENSE file to the project. Right now it is not open source!

For information about open source licenses, visit https://choosealicense.com/.

All previous contributors have to accept to license their contribution under the new license. If they don't accept or you can't reach them, you have to rewrite their code!

This get's harder the more contributors you have. So you should coordinate this ASAP!

When you start an open source project again, add a license first. Then a README!