Exercise 3.2 incorrect tf2 header files

[jrgnicho]

The exercise refers to tf2 headers which do not exists. The correct headers should be tf2_ros/...

[Chojins]

I also had to include the tf2_geometry_msgs.h to get it to build:

#include <tf2_ros/buffer.h>
#include <tf2_ros/transform_listener.h>
#include <tf2_geometry_msgs/tf2_geometry_msgs.h>