Update comments on allowable_encoder_error

We're setting a value outside the currently documented value for y2016.

Change-Id: Idc6ca14698b13d2b5ff02c3c00c29cffa53331ef
diff --git a/frc971/zeroing/zeroing.h b/frc971/zeroing/zeroing.h
index 5216df0..b5e2c14 100644
--- a/frc971/zeroing/zeroing.h
+++ b/frc971/zeroing/zeroing.h
@@ -116,8 +116,8 @@
   // Stores the position "start_pos" variable the first time the program
   // is zeroed.
   double first_start_pos_;
-  // Value between 0 and 1 which determines a fraction of the index_diff
-  // you want to use.
+  // The fraction of index_diff (possibly greater than 1) after which an error
+  // is reported.
   double allowable_encoder_error_;
 };