C++14 required?

[ToniRV]

Reporting the issue MIT-SPARK/Kimera-VIO-ROS#17 here, which seems to be the offending package.
I'll have a quick look myself and update this PR, but if you could give it a try at some point @yunzc that would be great! Thanks!

[ToniRV]

Ok, no clue why 😅
Nevertheless @yunzc can you take care of the following as well:

• Add License #2
• Add clang formate file
• Format the whole repo (it is quite inconsistent right now, and there are tabs and spaces everywhere 😢)
• Use pragma once in header files
• Call ros::spin(); in the main rather than in the ctor of visualizer
• Don't use long unsigned int unnecessarily. Best is if you typedef that with some conceptually meaningful name and then change to your convenience, perhaps a uint would be enough.
• Don't use auto unless really necessary, otw it will bring you more problems than solutions (and I think it might be the root cause of this issue).
• Can you also add a Readme: what is this repo doing and perhaps how to use it 👍