Consider removing requirement for .encrust.json if only running fatten sub-command

[joshwilson-dbx]

The encrust fatten command doesn't reference any of the data in the ~/.encrust.json file. This command is quite useful on it's own. While it's trivial to create an empty json file, not requiring it would make things easier for the end-user.

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In case the emoji wasn't clear, I would absolutely accept a PR doing this

[glyph]

I think there's still a bunch of refactoring to do here but this got addressed in a more generalized refactoring