Add a continuous absolute encoder zeroer

For swerve modules, we need to be able to zero a system where the
absolute encoder has a 1:1 ratio to the output and the output can spin
infinitely. Create an altered version of the AbsoluteEncoder zeroer to
do this.

Tests basically just steal from the absolute encoder tests, with an
extra test to check that it handles multiple revolutions correctly.

Change-Id: I0d2738499480f142bc5703de2c9cf6e345e3a896
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/frc971/zeroing/zeroing.h b/frc971/zeroing/zeroing.h
index f7b52a6..b0e6825 100644
--- a/frc971/zeroing/zeroing.h
+++ b/frc971/zeroing/zeroing.h
@@ -176,6 +176,7 @@
 // reverse dependencies to #include what they actually need...
 #include "frc971/zeroing/absolute_and_absolute_encoder.h"
 #include "frc971/zeroing/absolute_encoder.h"
+#include "frc971/zeroing/continuous_absolute_encoder.h"
 #include "frc971/zeroing/hall_effect_and_position.h"
 #include "frc971/zeroing/pot_and_absolute_encoder.h"
 #include "frc971/zeroing/pot_and_index.h"