Pull a particle from the queue and add it to the active list.

def __release_particle(self):
        """Pull a particle from the queue and add it to the active list."""
        # Calculate a potential angle for the particle.
        angle = random.randint(int(self.direction_range[0]), int(self.direction_range[1]))
        velocity = Vector2.from_polar(angle, self.particle_speed)

        physics = PhysicsObj(self.coords, Vector2(), velocity)
        particle = self.particle_pool.request_object()
        particle.initalize(physics)
        self.particles.append(particle)
        self.current_particle_count += 1