Codebase needs a style guide

There are a couple issues open right now that suggest a general restructuring of GAM code, which I agree would be good. However, one simple fix that would help both with code structure and readability of contributed code is a style guide that could be enforced during PR review.

The main file is over 13k lines, at this point, and lacks a consistent style and structure throughout, making it difficult for new contributors to even find their footing. There are several existing published style guides that could be utilized. I'm a bit biased, but I believe [Google's published Python style guide](http://google.github.io/styleguide/pyguide.html) is generally popular amongst different organizations. That said, I'd be happy with just about any choice at this point, as long as it improves the consistency.

Some examples of readability issues in current code:
- Lack of docstrings on most methods
- camelCase and snake_case inconsistency across variables and method declarations
- Really long character line limits causing horizontal scroll to be necessary, even on large displays
- Line break indentation inconsistency