make sure the config isn't missing keys when reading it

[teauxfu]

the way the configuration is currently interfaced with could be improved

keys are currently not validated

could probably trim the dependency on appdirs with an approach like this

https://github.com/pallets/click/blob/8b48450d5d63c747600e069d4c3e2274f41c8360/src/click/utils.py#L412

also see how poetry handles its config

[teauxfu]

an option is to move the config into a database table #24