Spec

This is a conversion from Google Docs to markdown so that we can do all development on GitHub and encourage other developers to contribute if they want to.

Please do not report spec typos or mistakes that also exist in the Google Doc in this review; they can be fixed later. Only verify that the markdown conversion from the Google Doc is maintained in the Markdown. If there are typos or other mistakes in the spec that also existed in the Google Doc, please file separate issues on Trello. If there is text missing or other conversion errors that indicate there is a wrong correspondence between the Google Doc and this markdown version, please **do** report them, as we want to spot them before we delete the original Google Doc.

This will allow a swift migration from Google Docs to GitHub and we will be able to get rid of the Google Doc.