Add withBody middleware to handle options root wrapper

If the query string parameter `include_root` is set to `false` then
don't wrap the response in a `result` wrapper. This only affects the
following routes:

- GET /:collection/:id
- PUT /:collection/:id
- POST /:collection

Any routes that list objects will not be affected by this parameter
because the pagination will use the root of the response to put
properties like `total` and `per_page` and `next` links.