Follow Cartographer API. (#49)

cartographer_turtlebot/configuration_files/turtlebot_depth_camera_2d.lua

@@ -43,7 +43,7 @@ TRAJECTORY_BUILDER_2D.ceres_scan_matcher.translation_weight = 70
 TRAJECTORY_BUILDER_2D.ceres_scan_matcher.rotation_weight = 300
 
 TRAJECTORY_BUILDER_2D.submaps.resolution = 0.035
-TRAJECTORY_BUILDER_2D.submaps.num_laser_fans = 120
+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.