update learner's group page with co_up info

[vsmart]

We have a new location for the learners group -- at co_up! 🎉

We should edit the learners group page to include:

• a link to their CoC http://co-up.de/code-of-conduct.html
• a link to their location info (with accessibility info etc) http://co-up.de/space-instructions.html

[lislis]

Started a PR here #56

[vsmart]

merged in #56