Document Controller:vibrate power argument;

Author: bjornbytes

docs/Controller:vibrate.md

@@ -7,11 +7,12 @@ Controller:vibrate
 
 Causes the Controller to vibrate.
 
-    controller:vibrate(duration)
+    controller:vibrate(duration, power)
 
 ### Arguments
 
 - `number duration` The amount of time to vibrate the Controller, in seconds.
+- `number power (1)` The strength of the vibration, between 0 and 1.
 
 ### Returns
 
@@ -20,5 +21,6 @@ Nothing
 Notes
 ---
 
-On the HTC Vive, the value for `duration` currently must be less than .004 seconds.  Call this
-function several frames in a row for stronger or prolonged vibration patterns.
+On the HTC Vive, the value for `duration` currently must be less than .004 seconds, and the `power`
+is always set to 1.0.  Call this function several frames in a row over several frames for stronger
+or prolonged vibration patterns.