On `connect`, create a new tmux session and move the relevant window in about overmind

[canadaduane]

Ok, here's a solution:

I added the following to overmind.tmux.conf (the tmux config that we load via the -F switch, e.g. overmind start -F scripts/overmind.tmux.conf):

set-hook -g client-attached "run 'sess=\`tmux new -d -P -t \"#{session_name}\"\` && tmux switch-cli -t \"\${sess}#{window_index}\"'"

Whenever a new client attaches, this creates a new session within the same overmind session-group (a session-group shares all windows within all sessions), and switches to the same window_index as was current before creating the new session.

This is allows us to open a different "current window" in each new Terminal tab.