Negotiate Docker Version

Yeah v2.0.3 was also supposed to do this, but I made code soup while I was trying to test the pull request I think
I'm not entirely sure what happened there. Did I imagine handling this already??

What's Changed

• Added clarifications by @heisenberg2980 in #25
• Added API version negotiation to group.go by @technotiger in #28

New Contributors

• @heisenberg2980 made their first contribution in #25

Full Changelog: v2.0.3...v2.0.4