Provide support for processing requests

[sjkaliski]

The package only focuses on the presentation/ETL layer (how the response looks). It should also bring "up to date" a request at an older version.

Example:

POST /items at 2018-01-01 submits

{
  "title": "foo"
}

But at 2018-03-01 aka master

{
  "name": "foo"
}

The package should convert title -> name, allow API to process the request, and then convert name -> title.

[codyaray]

Each action needs two parts, right? A migrate up and a migrate down