tmux: play nice with iTerm2
tmux: play nice with iTerm2

That is, don't use reattach-to-user-namespace. iTerm2 provides an option to
allow applications in the terminal to access the clipboard, as well as deeper
shell integration utilities, which obviate the need for
reattach-to-user-namespace. What's more, iTerm2's tmux integration doesn't work
with it, nor when aggressive-resize is on.

See also:

- https://iterm2.com/documentation-preferences.html
- https://iterm2.com/documentation-utilities.html
- https://iterm2.com/documentation-tmux-integration.html
- https://github.com/tmux-plugins/tmux-sensible/issues/24

LnL7/nix-darwin