have cli log `vak` version

[NickleDave]

i.e. should be in log file from each run

[NickleDave]

I looked at this but it is currently not easy since each function in cli sets up a logger separately, e.g. prep instantiates one, so does train, etc.

Might be a good reason to have a Logger class that does things on setUp like log the version and / or current git commit