Reorder things in .zshrc to avoid overwriting own keybindings.
Use fancy "-Z2" flag create integers with leading zeroes inside prompt.

Very cool.
Fix some broken prompt bits from major ZSH overhaul.
Replace dozens of global prompt variables with a single global hash.

Cleans things up nicely.
Make default tmux session name the current user's name.
Make tmux use TERM=screen-256color if 256 colors are actually available.

The general idea is stolen from oh-my-zsh, but my implementation is
less fancy.
Change prompt's Unicode support detection.

The latest tmux changes mean I'm better able to tell when I'm running
in a fancy terminal app versus a Linux virtual console.