remove duplicate connection code 'OrientDb::Client.instance' to use Base class 'connection' method.

app/repositories/orient_db/edge_repository.rb

@@ -6,7 +6,7 @@ module OrientDb
     end
 
     def create_edge(edge_class, from_id, to_id)
-      OrientDb::Client.instance.command "CREATE EDGE #{edge_class} FROM #{from_id} TO #{to_id}"
+      connection.command "CREATE EDGE #{edge_class} FROM #{from_id} TO #{to_id}"
     end
 
   end