Doing a step in the simulation

Property definitions

	# Doing a step in the simulation
	fun do_step do
	end

lib/actors/examples/agent_simulation/agent_simulation.nit:50,2--52,4

	redef fun do_step do
		for o in others do
			o.async.greet("Hello !", self)
			count += 1
		end
	end

lib/actors/examples/agent_simulation/simple_simulation.nit:35,2--40,4