Default Tmux Attach and Fish Shell

Tmux now reattaches on launch, and also uses the fish shell. I still
need to comment out the tmux config but i am just making it usable
currently, not "customized"
Bound Detach Others to an Easy Bind

Since any new terminals, laptop connections, etc, will never close
themselves, tmux will think they're all still open. Normally this
doesn't matter, but if my laptop is open and i want to use my desktop
this drives me mad. So now, i can kill my laptop sessions with `C-b D`,
and the default for that has been reassigned to `C-b C-d`.