07-items Carrying, Grabbing, and Dropping Items

On this version you're able to carry, grab, and drop items. Items are
set with refs within room and thread local *inventory* refs for player's
inventory

  * Added *inventory* ref and move it to player.clj
  * Move all dynamically bound refs to player.clj
  * Add items to rooms [rooms.clj]
  * Adding `pick` and `drop` commands to player [commands.clj]
  * Updated look command [commands.clj]