onCollision() {
		return false;
	}
onCollision callback, triggered in case of collision,
when this renderable body is colliding with another one
@param {ResponseObject} response - the collision response object
@param {Renderable} other - the other renderable touching this one (a reference to response.a or response.b)
@returns {boolean} true if the object should respond to the collision (its position and velocity will be corrected)
@example
// colision handler
onCollision(response) {
    if (response.b.body.collisionType === me.collision.types.ENEMY_OBJECT) {
        // makes the other object solid, by substracting the overlap vector to the current position
        this.pos.sub(response.overlapV);
        this.hurt();
        // not solid
        return false;
    }
    // Make the object solid
    return true;
},