Improve intaking.

Add a stuck box detector (box intake velocity), and better handling for
boxes coming in sideways.

Change-Id: I5fa4a5b00f7dd1288f8fed33375953bdfe710559
diff --git a/y2018/control_loops/superstructure/intake/intake.h b/y2018/control_loops/superstructure/intake/intake.h
index 2c36efa..e570c50 100644
--- a/y2018/control_loops/superstructure/intake/intake.h
+++ b/y2018/control_loops/superstructure/intake/intake.h
@@ -97,6 +97,8 @@
     return controller_.output_position() < -0.1;
   }
 
+  double output_position() const { return controller_.output_position(); }
+
  private:
   IntakeController controller_;