Estimate which way is down in Python

Change-Id: I5aaac2c7aaaa7758d69e46a76610842a91b608d6
diff --git a/frc971/control_loops/python/BUILD b/frc971/control_loops/python/BUILD
index d172983..897738a 100644
--- a/frc971/control_loops/python/BUILD
+++ b/frc971/control_loops/python/BUILD
@@ -26,3 +26,13 @@
     ':controls',
   ],
 )
+
+py_binary(
+  name = 'down_estimator',
+  srcs = [
+    'down_estimator.py',
+  ],
+  deps = [
+    ':controls',
+  ],
+)