Start a style guidelines for text and code

[bucko13]

We had a good suggestion in #229 to formalize currency display around a specific standard. We don't have anything formally set in stone to hold ourselves or contributors to either way and so I think it would be good to start with those guidelines and then apply them where applicable.

• Regression (a behavior that used to work and stopped working in a new release)
• Bug report
• Feature request
• Documentation issue or request
• Support request