GitLab

Brings the "Running" section up to date and mentiones the new flag
"benchmark-generators"

Publish the most recently built linux binaries as artifacts. This makes
the wait shorter for users who just want to try copar quickly.

Also add a link to the artifacts in the readme

This introduces the new sub-command `refine` that does what running the
binary without sub-command previously did.

This opens up the possibility for further sub-commands and improves
discoverability.