gitlab-ci: update dockerfile and use tags to use runner with good image

See merge request !15

Fix log issue at end of the script and allow empty contacts

See merge request !14

V2.1 acme draft 16, ready order status, general rework

See merge request !13

key rollover has been completely updated (acme has changed way to rollover and we needed to clarify better the code variable names)

Too many languages for me today: HTML, TSQL, C# and now Python 3 :D

config_factory: Let's Encrypt staging API refuse to create account with contact linked to "@example.com" domain.

That's make even more sense as there's no "finalize" object, but just a "finalize" URL.

V2 : Support of Let's Encrypt API v2

See merge request !12

v2: dnspython is a stub resolver, so self-check TXT record query needs to happen on a non-CNAME record

This reverts ada9f449 as suggested and
explained on Github PR #1