Add include support

[avelosa]

Tried to implement supporting the include functionality that is traditionally specified as a query parameter. The include feature is defined here.
Since there are multiple operations this implementation lets the api user specify a meta object at the top level of each individual operation data. In the meta object the api user can set the include field that expects a list of relationship names.

Example Request Data:

{
  "atomic:operations": [
    {
      "op": "add",
      "data": {
        "type": "Book",
        "attributes": {
          "title": "Meditations"
        },
        "relationships": {
          "author": {
             "data": {
               "id": "1",
               "type": "Author"
             }
          }
        }
      },
      "meta": {
        "include": ["author"]
      }
    }
  ]
}

Example Response Data:

{
  "atomic:results": [
    {
      "data": {
        "type": "Book",
        "id": "1",
        "attributes": {
          "title": "Meditations"
        },
        "relationships": {
          "author": {
             "data": {
               "id": "1",
               "type": "Author"
             }
          }
        }
      }
    },
    "included": [
      {
        "data": {
          "id": "1",
          "type": "Author",
          "attributes": {
            "first_name": "Marcus",
            "last_name": "Aurelius"
          }
        }
      }     
    ]
  ]
}

Each operation can use the include parameter if desired. The meta field is of course optional.

Also adds unit tests for the view and parser.