Investigate using Vulture to find dead code

[jzohrab]

https://pypi.org/project/vulture/ looks like a potentially useful tool.

I believe that pylint is already finding unused vars, but it's not finding dead code.

I guess vulture would need to ignore all of the flask endpoints, as they're only called when needed.

The vulture pip dependency should be added to the requirements-dev.txt file. Some config can likely be added ... somewhere.