Renamed ZeroingEstimator to PotAndIndexPulseZeroingEstimator

Renamed to allow for creating a new interface named ZeroingEstimator
in the future.

Change-Id: I374808cdc39dd4141ea67c81de69bbac98326648
diff --git a/y2015/control_loops/claw/claw.h b/y2015/control_loops/claw/claw.h
index 324f9f3..e7523eb 100644
--- a/y2015/control_loops/claw/claw.h
+++ b/y2015/control_loops/claw/claw.h
@@ -95,7 +95,7 @@
   // Latest position from queue.
   control_loops::ClawQueue::Position current_position_;
   // Zeroing estimator for claw.
-  ::frc971::zeroing::ZeroingEstimator claw_estimator_;
+  ::frc971::zeroing::PotAndIndexPulseZeroingEstimator claw_estimator_;
 
   // The goal for the claw.
   double claw_goal_ = 0.0;