link to Modoboa in README
ensure Python operates in UTF-8 with a consistent locale for all users

fixes #206 (hopefully)
dns_update: assume DKIM is present
add strict SPF and DMARC records to any subdomains (including custom records) that do not have SPF/DMARC set

closes #208
typo in roundcube download URL

see https://github.com/mail-in-a-box/mailinabox/commit/8e0967dd8e2ecce6a1092deaca7241a6d927ae1e#commitcomment-7940724