def outset_bisectors(length)
	    vertices.zip(spokes).map {|v,b| b ? Edge.new(v, v+(b * length)) : nil}
	end
def outset_bisectors(length)
	    vertices.zip(spokes).map {|v,b| b ? Edge.new(v, v+(b * length)) : nil}
	end
Vertex bisectors suitable for outsetting
 @param [Number] length    The distance to offset by
 @return [Array<Edge>]	{Edge}s representing the bisectors