Don't log mtrx9.controllers.matrices.update requests.

The rest of the implementation is lightweight; logging each request is
relatively quite expensive. Also, we probably don't really care what's
being sent, as it's being relayed to browsers directly, and there's no
storage.
Update README, simplifying extensively.
Bump version to v1.2.0 .
Update project description and URL.
Merge branch 'release/v1.2.0'