Basic AI system with wandering.

Also begin work on an allegiance-based system for humans.
Factioning system and faction display
Change background color in play.

Add some test units from different factions.
Assign the player to the MERRY_MEN faction
Random seeding on love.load
Pull out redundant code in archer.lua
Much improved AI algorithm.

The algorithm now has two modes of operation: wander and hostile. I made
the decision to use these two modes instead of my original idea of three
(wander, ally, and hostile) because I realized that the factions would
provide enough information for an NPC to decide whether it was friendly or
not.

Accordingly, NPCs will not attack once set to "wander" mode. If left alone
while in hostile mode, they will revert back to wandering mode. While in
hostile mode, they will move frequently and shoot towards the nearest
enemy.
Proper angular movement for NPCs
Angular movement for the player.
Add another NPC to the scene.
Fix type assertion in play.lua
Merge pull request #6 from ac7/npc_logic

Npc Logic