Improve queries

If the user requested authors with their quotes, it did one query
to get the authors and then one query per each author to get his
quotes. Now it loads everything in the first query, then just
checks if it is already loaded and that is all.

Resolves #13

graphql/queries/author/authors.js

@@ -23,6 +23,6 @@ export default {
     const limit = args.first || 10;
     delete args.offset;
     delete args.first;
-    return models.author.findAll({where: args, offset, limit});
+    return models.author.findAll({where: args, include: [ { model: models.quote } ], offset, limit});
   }
 };

graphql/types/author.js

@@ -38,6 +38,9 @@ export default new GraphQLObjectType({
                 type: new GraphQLList(Quote),
                 description: "author's quotes",
                 resolve(author) {
+                    if (author.hasOwnProperty('quotes')) {
+                      return author.quotes;
+                    }
                     return models.quote.findAll({ where: { author_id: author.id } });
                 }
             }

graphql/types/quote.js

@@ -23,6 +23,9 @@ export default new GraphQLObjectType({
                 type: Author,
                 description: "author of this quote",
                 resolve (quote) {
+                    if (quote.hasOwnProperty('author')) {
+                      return quote.author;
+                    }
                     return models.author.findById(quote.author_id);
                 }
             },