First Try

robot.js

var Robot = function(robot) {
//\  robot.clone();
//  this.mode = 'scanning';
};

var mode = 'scanning';
var targetVector = 0;

var lastFired = 0;
var iteration = 0;

Robot.prototype.onIdle = function(ev) {
	var robot = ev.robot;
  iteration++;
  if (mode == 'scanning') {
    robot.rotateCannon(20);
  }
  if (mode == 'targetting') {
    var d = robot.cannonAbsoluteAngle - targetVector;
    if (d < 0) {
	    robot.rotateCannon(10);
    } else {
	    robot.rotateCannon(-15);
    }
    robot.ahead(20);
  }
  if (iteration - lastFired > 2) {
    mode = "scanning";
  }
};

Robot.prototype.onRobotCollision = function(ev) {
  var robot = ev.robot;
  robot.back(100);
};

Robot.prototype.onWallCollision = function(ev) {
  var robot = ev.robot;
  robot.turn(ev.bearing - 90);
};

Robot.prototype.onHitByBullet = function(ev) {
  var robot = ev.robot;
	robot.turn(90 - ev.bulletBearing);
};

Robot.prototype.onScannedRobot = function(ev) {
  var robot = ev.robot;
  if (robot.id == ev.scannedRobot.parentId) {
    return;
  }
  if (robot.parentId == ev.scannedRobot.id) {
    return;
  }
	robot.fire();
  lastFired = iteration;
  mode = 'targetting';
  targetVector = robot.cannonAbsoluteAngle;
};