Update README.md

Added documentation of new pilot keys introduced by @jedwood

README.md

@@ -69,9 +69,13 @@ bower install
 If you have enabled the **pilot** plugin, you can fly the drone with the following keys. You can define your keyboard in the 
 config file. In the plugin, `azerty` and `qwerty` keyboards are defined.  Feel free to define others.
 
-Use `Z, S, Q, D` to move front, back and sideways. Use your `cursors` to go up/down or turn
+Use `z, s, q, d` to move front, back and sideways. Use your `cursors` to go up/down or turn
 clockwise/counter clockwise. Use `t` to takeoff and `l` for landing.
 
+Use the `tab` key to toggle acceleration speed slow/fast.
+
+Use the `f` key to perform a flip in the current direction of movement.
+
 ### Record a mission
 
 Just press the `r` to start recording. A popup alers you when the recording starts. Press `r` again to stop. Each mission