Tmux: prevent selecting panes from eating next direction key

In Tmux, when bouncing between panes, I almost always only want to go
one pane at a time. Oftentimes I want to do something with my direction
keys immediately after switching panes, but because tmux has repeating
on by default, a direction key pressed immediately after selecting a
pane will tell Tmux to try to select another pane.

Thankfully, I can disable the repeat option by rebinding these keys
without it [1].

[1]: http://superuser.com/a/325579