Conduct comprehensive code review

[helrond]

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

The code in this app has not been reviewed for a while, and with a fresh set of eyes, there are a number of things that could be improved.

Describe the solution you'd like

Conduct a comprehensive code review of this application and address any issues. A couple of obvious things:

• Exception handling in the main run method could be improved - the custom exceptions aren't really all that useful
• places where variables are assigned to the instantiated class for no good reason (cleanup routine)
• places where existing asterism helpers could be used (helpers)
• Improve docstrings across application

[bonniegee]

Not sure if this should be a separate issue, but I think the fixtures (particularly those that represent JSON from Aurora) should be reviewed as well.