Add Climber class and tests

For now, it is a simple pass through.

Change-Id: I5274b03f6ade23fbc98713cf8ed849866a85b429
diff --git a/y2020/control_loops/superstructure/superstructure.cc b/y2020/control_loops/superstructure/superstructure.cc
index eb88e93..c2512db 100644
--- a/y2020/control_loops/superstructure/superstructure.cc
+++ b/y2020/control_loops/superstructure/superstructure.cc
@@ -52,6 +52,8 @@
           output != nullptr ? &(output_struct.turret_voltage) : nullptr,
           status->fbb());
 
+  climber_.Iterate(unsafe_goal, output != nullptr ? &(output_struct) : nullptr);
+
   bool zeroed;
   bool estopped;