Added growth requirement for seed.
Skeleton for rabbit and flower. Cleaning up unit code.
Merge remote-tracking branch 'carly/master'
Flower functionality now in its own class.
Component-like design with a key-event manager.
Merge branch 'flowers_and_rabbits'

Conflicts:
	terrain.py
	unit.py
Action units implemented. Gives mechanics more flexibility.
Added more png files for root, thorn, and vine