Fix documentation in fridge.q and actions.

Austin made zero on the arm sticking straight up, and the comments
in fridge.q ended up being wrong. I fixed these comments, as well
as the actions that I had written based on them.

I also made the comments in fridge.q about zero on the elevator
match the ones in constants.cc.

Change-Id: Ie50c99f6cafc82f0e4baba851cd20353a9d871ac
diff --git a/frc971/actors/stack_actor.cc b/frc971/actors/stack_actor.cc
index ff9c739..6ce8fbd 100644
--- a/frc971/actors/stack_actor.cc
+++ b/frc971/actors/stack_actor.cc
@@ -28,7 +28,7 @@
   params.elevator_max_velocity = kElevatorMaxVelocity;
   params.elevator_max_acceleration = kElevatorMaxAccel;
 
-  params.arm_angle = M_PI / 2.0;
+  params.arm_angle = 0.0;
   params.arm_max_velocity = kArmMaxVelocity;
   params.arm_max_acceleration = kArmMaxAccel;