To use: From the top directory, run `irb -r ./lib/app.rb`

The following commands are available:

box
  Prints out the state of the puzzlebox
  
move <x>, <y>, <z>
  Occupies the space (x,y,z)
  
undo
  Undoes your last move
  
restart
  Undoes all moves for this puzzlebox and restarts the puzzle in the initial state.
  
create <x>, <y>, <z>, <side>
  Creates a puzzle with a goal at (x,y,z) on a box with dimensions <side> x <side> x <side>