allow users to pass the config.json location by env var/argument

[drewwells]

The examples with -p on the command line make me really wary. This is leaking passwords in people's history and process table. Any other user on the system can see the password in this case.

Enable the ability to specify the config.json location as env var and cli argument so multiple config.json can be used and a custom location can be used. This is nice for setups where $HOME may not be ideal.