Add RequireInitialization = 1 to NumTraits::Jet.

Thanks to Nima Kevian for reporting this.

Change-Id: I9c45f4cabc8d5ce246c2a6ebe102161c6a771df5

include/ceres/jet.h

diff --git a/include/ceres/jet.h b/include/ceres/jet.h
index 4d2a857..7907b98 100644
--- a/include/ceres/jet.h
+++ b/include/ceres/jet.h
@@ -740,7 +740,8 @@
     AddCost = 1,
     // For Jet types, multiplication is more expensive than addition.
     MulCost = 3,
-    HasFloatingPoint = 1
+    HasFloatingPoint = 1,
+    RequireInitialization = 1
   };
 };