Make the robust curve fitting example robust.

Change-Id: Iffcde8f168b7cd68e56f351c43088d7aef1e5e2f

examples/robust_curve_fitting.cc

diff --git a/examples/robust_curve_fitting.cc b/examples/robust_curve_fitting.cc
index 65da4e5..67aca03 100644
--- a/examples/robust_curve_fitting.cc
+++ b/examples/robust_curve_fitting.cc
@@ -147,7 +147,9 @@
     CostFunction* cost_function =
         new AutoDiffCostFunction<ExponentialResidual, 1, 1, 1>(
             new ExponentialResidual(data[2 * i], data[2 * i + 1]));
-    problem.AddResidualBlock(cost_function, NULL, &m, &c);
+    problem.AddResidualBlock(cost_function,
+                             new CauchyLoss(0.5),
+                             &m, &c);
   }
 
   Solver::Options options;