API documentation improvements

_WORK IN PROGRESS_

This adds:
* A proper introduction
* "Getting Started" example
* `s/ryan.com/example.com/` (sorry, Ryan)
* minor rake task bugfixes
* other typo fixes and the bringing-up-to-date of things
Why `login_required=true`?  And any way we can use the local server's base URL since this is a partial in Rails?