maintains a jump-list of directories you actually use
old directories eventually fall off the list
inspired by Joel Schaerer's http://wiki.github.com/joelthelion/autojump
and something similar i had - but i could never get the dir list right.

INSTALL:
  source into .bashrc under your '[-z "$PS1" ] || return' line
  cd around for a while

USE:
  j [--l] [regex1 ... regexn]
    regex1 ... regexn jump to the most used directory matching all masks
    --l               show the list instead of jumping
                      with no args, returns full list