Before executing a wrap-around-corner, make sure we truly have enough room to complete it
Rename client and server files, and delete chipmunk_utilities.rb
Collapse NPC into Entity, and also make Entity the namespace for NPCs (all entities except Players).  Define two types, Block and Titanium (the latter is basically immutable), and let the player select which to create.  New dependency on gem 'facets'
Add --profile and --self-check to Game.  The first turns on profiling so we can see how long each update takes (but screws with the timing).  The second turns on consistency checks of the GameSpace; turning this off definitely means the server doesn't have to work as hard