Cells lose energy equal to their walking force every instance they exert energy. (This is currently a very small amount.)
Cells' force exerted is now also reset after it is used to calculate acceleration, so that cells don't have to manually reset it whenever they actively choose not to accelerate.
Gave 'derp_force' an appropriate name.
Messing with multi-line docstrings so nano stops being stupid
Noticed raidus and energy were assigned twice, so that redundancy has been removed.
Merge branch '0.4.dalen' into 0.4

Conflicts:
	cells.py