Add Support for Config Through CLI Args and Env Vars

[danehans]

#111 specifies that EG will only be configured through a config file. This is a tracking issue to capture requirements for adding CLI args and possibly env var support for configuring EG.

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in the next 7 days unless it is tagged "help wanted" or "no stalebot" or other activity occurs. Thank you for your contributions.

[danehans]

Closing since #146 added an initial arg for specifying the path to the config file.