Add support for JSON API

[eleonoraortega]

Parser does not recognise the media type designation of JSON API (application/vnd.api+json)

Example:

#%RAML 1.0
title: Anypoint Service Registry
baseUri: http://registry-qa.mulesoft.com/api/console/
resourceTypes:
  - organizationsCurrentOwnersUsername:
      usage: Retrieve details for an owner
/organizations/current: 
  get: 
    responses: 
      200: 
        description: OK
        body: 
          application/vnd.mulesoft.habitat+json:  
      400: 
        description: Mandatory query string parameter not being provided
      415: 
        description: The content type of the body is not supported
      404: 
        description: The organization cannot be found
      500: 
        description: Database current unavailable

Error:

• Unexpected key 'application/vnd.mulesoft.habitat+json' [line=13, col=11]

[svacas]

fixed by 231733c679f373f958a96affb0ea60eacf75edc2