Merge branch 'master' of https://github.com/microsoft/pxt-ev3

docs/coding.md

@@ -167,4 +167,5 @@
   "description": "Activity 2",
   "url":"/coding/roaming-2",
   "cardType": "example"
-}, {
+}]
+```

docs/examples/line-follower-pid.md

@@ -0,0 +1,16 @@
+
+```blocks
+let lasterror = 0
+let D = 0
+let I = 0
+let P = 0
+let error = 0
+loops.forever(function () {
+    error = sensors.color3.light(LightIntensityMode.Reflected) - 35
+    P = error * 5
+    I = I + error * 0.01
+    D = (error - lasterror) * 0.2
+    motors.largeBC.steer(P + (I + D), 100)
+    lasterror = error
+})
+```