[S2GRAPH-204] Avoid N + 1 queries in GraphQL

JIRA:
  [S2GRAPH-204] https://issues.apache.org/jira/browse/S2GRAPH-204

Pull Request:
  Closes #157

Author
  daewon <daewon@apache.org>

CHANGES

@@ -67,8 +67,9 @@ Release Notes - S2Graph - Version 0.2.0
     * [S2GRAPH-170] - Create Interface for S2Edge/S2Vertex/S2Graph.
     * [S2GRAPH-182] - Version up spark dependencies.
     * [S2GRAPH-198] - Skip json Decode error and continue.
-    * [S2GRAPH-200] - docker image could not include extra jars.
     * [S2GRAPH-199] - Changing query more intuitively by using `columnName` instead of `from/to` in label field name.
+    * [S2GRAPH-200] - docker image could not include extra jars.
+    * [S2GRAPH-204] - Avoid N + 1 queries in GraphQL
 
 ** New Feature
     * [S2GRAPH-123] - Support different index on out/in direction.