Including Resources should be by name not type

[brainwipe]

Found in #35, when including a resource, it should be the relationship name that is used and not the type. Using the json:api example of blog/author:

GET /articles?include=author

{
  "data": [{
    "type": "articles",
    "id": "1",
    "attributes": {
      "title": "JSON API paints my bikeshed!"
    },
    "links": {
      "self": "http://example.com/articles/1"
    },
    "relationships": {
      "author": {
        "links": {
          "self": "http://example.com/articles/1/relationships/author",
          "related": "http://example.com/articles/1/author"
        },
        "data": { "type": "people", "id": "9" }
      },
    }
  }],
  "included": [{
    "type": "people",
    "id": "9",
    "attributes": {
      "first-name": "Dan",
      "last-name": "Gebhardt",
      "twitter": "dgeb"
    },
    "links": {
      "self": "http://example.com/people/9"
    }
  }
}

In ResourceMapping.cs the line:

var relationship = currentMapping.Relationships.SingleOrDefault(x => x.RelatedBaseResourceType == part);

Should be checking against a resource name not the underlying type.