Codify guidelines about how this documentation works

[underscorefunk]

Add a readme with some details to set context for these docs.

1. These docs will try to follow the same principles we follow when writing applications.

• We can't use ideas that aren't brought into scope
• We must define all ideas in the system if they're being discussed
• Employ stratified design of layers of understanding

2. Assume no prior knowledge
3. Express the context in which the documentation is being written, and who it's being written for. The implications of this should be made clear to the reader.