Add ball detector and only intake if we have a ball.

Change-Id: Id72dde414d6dcddd8721056efdee3e5f25900a3a
diff --git a/y2016/queues/ball_detector.q b/y2016/queues/ball_detector.q
new file mode 100644
index 0000000..948cc25
--- /dev/null
+++ b/y2016/queues/ball_detector.q
@@ -0,0 +1,13 @@
+package y2016.sensors;
+
+message BallDetector {
+  // Voltage measured by the ball detector sensor.
+
+  // Higher voltage means ball is closer to detector, lower voltage means ball
+  // is far from the sensor or not in the robot at all.
+  // TODO(comran): Check to see if our sensor's output corresponds with the
+  // comment above.
+
+  double voltage;
+};
+queue BallDetector ball_detector;