tmux: add more comments indicating defaults
tmux: add more comments indicating defaults

When I'm pairing with somebody else using their .tmux.conf I often have
trouble remembering what the default bindings are for the things that I
have overridden in my own .tmux.conf.

Mention the default settings in comments; maybe eventually they'll sink
in.

Signed-off-by: Wincent Colaiuta <c76ac2e9cd86441713c7dfae92c451f3e6d17fdc@wincent.com>

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent