ProtonMail - remove forced signature

This userscript applies to https://mail.protonmail.com and https://beta.protonmail.com/ (for the 'beta' subdomain it only works in Chrome, see #13 ).
It automatically removes the ProtonMail signature from the 'New message' textboxes,
which is appended by default to each mail body and cannot be modified via Settings in free accounts.

It uses the excellent library arrive.js

Tampermonkey and Violentmonkey are supported - Greasemonkey is not supported.

Hosted at GitHub