Rewrite several sections of README.
Add @riseup.net to EMAIL_DOMAIN[S|_RULES|_MAP] settings.
Add riseup.net to HTTPS "I need an alternative way of getting bridges!".
Fix twisted.python.versions.Version import; upstream moved the class.
Update translations for email provider strings by hand.

Since it's a single "%s, " that was added to the string for email providers,
I've update every single english string and all of their translations by
hand. This will save us losing those translations (otherwise they'd all
fallback to English!), but Transifex and the automation scripts are probably
going to get mad at me that I updated the strings myself. Fuck Transifex.
Update gettext .pot template file with string changes for email providers.
Merge branch 'fix/11139-riseup_r1' into develop