Misc programming recommendations

[lukpueh]

#21 drastically shortens our custom python guideline document, referencing an external guide instead of replicating common rules and removing very particular programming recommendations, with the goal of lowering maintenance and contribution barriers.

Here are some references to discarded items that might be worth resurrecting in case we ever want to add a misc programming recommendation document in the future:

• Replace styleguide with Google guide supplement #21 (comment)
• Replace styleguide with Google guide supplement #21 (comment)
• 6ea78bc
• Arrowhead anti-pattern in examples #3
• Unreachable else best practice #18