lcd - lazy change directory.  key => directory shortcut mappings.

Add this to your bash .profile, it will define the following aliases:
 - acd <key>: Add a mapping from the current directory to the key |key|.
 - lcd <key>: Jump to the directory mapped with the key |key|.
 - pcd: Print all key / directory mappings.
 - dcd <key>: Delete a mapping.

The mappings are stored in ~/.lcdrc.  This file will initially be created
when you use the acd command.  lcd's biggest feature is it's simplicity, it
is implemented in a few lines of bash, reusing existing fast tools.  The
mapping file is very simple, easy to share / merge between machines, etc.

Example usage:
  $ cd /some/really/long/path/that/is/annoying/to/type
  $ acd long  # Create a mapping from current directory to the key "long".
  $ cd  # Change back to your home directory, or somewhere else.
  $ lcd long  # Change to the really long annoying path.