Follow googlecartographer/cartographer#307. (#56)

Also fix the configuration file test, following googlecartographer/cartographer_ros#346.

cartographer_turtlebot/cartographer_turtlebot/configuration_files_test.cc

@@ -38,6 +38,7 @@ TEST_P(ConfigurationFilesTest, ValidateNodeOptions) {
     ::cartographer::common::LuaParameterDictionary lua_parameter_dictionary(
         code, std::move(file_resolver));
     ::cartographer_ros::CreateNodeOptions(&lua_parameter_dictionary);
+    ::cartographer_ros::CreateTrajectoryOptions(&lua_parameter_dictionary);
   });
 }
 

cartographer_turtlebot/configuration_files/turtlebot_depth_camera_2d.lua

@@ -49,6 +49,5 @@ TRAJECTORY_BUILDER_2D.submaps.num_range_data = 120
 SPARSE_POSE_GRAPH.optimize_every_n_scans = 120
 SPARSE_POSE_GRAPH.constraint_builder.min_score = 0.82
 SPARSE_POSE_GRAPH.constraint_builder.sampling_ratio = 1.
-SPARSE_POSE_GRAPH.constraint_builder.ceres_scan_matcher.covariance_scale = 3e-5
 
 return options