Some find on issue #8 and ROS Noetic build

[weemma]

First of all, thank you for amazing projects.

I managed to run your LMPCC successfully after some debugging and thus I want to share the way I did it (solve #8).

#10 and bbrito/pedsim_ros#1 are what I've done about it.
Although I modified it for running in Ubuntu 20.04 ROS Noetic, I think the modifications are irrelevant to the ROS version so it should work in ROS Melodic or ROS Kinetic too.

I hope it helps.