Headers shown in methods

[dajinchu]

Reposting #469 with the right branch

Headers set from a resource_description are now inherited in each of the resource's methods, and are no longer displayed under resource.

Example:

resource_description do
  short 'Test case data'
  formats ['json']
  header 'X-API-EMAIL', 'user\'s email', required: 
  header 'X-API-TOKEN', 'user\'s current authentication token', required: true
end

Used to show:

It now looks like:

where every method of document shows the headers.

[mathieujobin]

can you update your branch to resolve the conflicts?