tmux session scripts, pilfered from: http://blog.edsantiago.com/articles/tmux-session-preserve/

TODO
 * Using PROMPT_COMMAND to flush history after each command (e.g. to survive crashes).
  * (I think this might be done?)
 * Finding a way to handle new windows created via ESC-c (which will be called "bash" by default).
 * Handling window renames (probably via .logout)