Allow players to have a name
Clean up and refactor bidirectional connections in seeds.rb
Model and interface to permit buying items from NPCs
Allow players to buy from NPCs; add inventory
Allow items to be used; implementing health potions
Try fix weird combat_log sync issues across actions

Occasionally a combat_log or error would hide for one request and then
display in the next request; instead of trying to store a singleton value
through combat_log(), we instead use the session store directly and add a
new clear_combat_log() helper that we call procedurally, once the combat
log has been rendered.
Restock NPCs selling; display inventory count