Better error handling cleanup

[sugarmanz]

Is your feature request related to a problem? Please describe.

When auto fails, it should revert/cleanup any changes or commits it made.

Ex: when I have uncommitted changes and run auto, it will create a CHANGELOG commit, but then fail out when it detects the issue. Unfortunately, the CHANGELOG commit stays around.

Describe the solution you'd like

Plugins should tap into a cleanup hook to provide functionality to revert any changes it made.

Describe alternatives you've considered

Potentially, auto core could do all the cleanup, but that would be difficult depending on the different functionality of plugins.

[hipstersmoothie]

One part of this will be removing process.exit from any plugin or core. They should just throw an error that we catch in the cli and exit.