Revert "Change channel subscription to happen in groups (#1166)"
Revert "Change channel subscription to happen in groups (#1166)"

This reverts commit 0744e3b8ad3dbe7cf04049ecb45ca3035f144885.

We had reports of 500 errors when hitting the `pusher/auth` endpoint
and were able to isolate the errors to this commit. Not sure exactly
what's happening, but reverting in the interim while we investigate
further.

See https://github.com/travis-pro/team-teal/issues/2117 for more
details.

travis-ci/travis-web,travis-ci/travis-web,travis-ci/travis-web,travis-ci/travis-web