updated default map (4 squares)
Merge pull request #1 from dckuehn/master

dckuehn: Added tank sprite
updated tank sprite image paths
added url path for correcting sprite image paths
corrected sprite image paths
added basic object drawings in addition to sprites
adjusted tank size to match sprite size
added canvas save/restore around sprite drawings
added bootstrap, alerts, click to spawn, self destruct, and improved multiplayer functionality

-added bootstrap (and jQuery)
-improved multiplayer handling (separate player and tank objs)
-added alerts
-added click to spawn
-added self destruct
-added session id to interface
-renamed client side socket object
removed drawing tank collision box
added more kill messages
set default tank angle to 0
added tank and map objects polygons (to eventually improve collisions)
Edited sprites to have turretless tank and turret separate from each other.  Edited javascript to utilize these sprites.