Summary of recent changes

["Edward J. Yoon" <ed...@apache.org>]

Hi all, here's summary of recent changes.

1) Added the sort option to "PartitioningRunner" (merge sort was
used). With this, DiskVerticesInfo is now enabled.

2) Every in-memory verticesInfo implementations are now uses the
Vertex object serialization.

3) Added the MapVerticesInfo which stores the vertices into
memory-based tree map.

 - ListVerticesInfo - stores the sorted vertices into a array list.
 - MapVerticesInfo - stores the vertices into a tree map.
 - DiskVerticesInfo - stores the sorted vertices into a local file.

Only MapVerticesInfo allows the runtime graph modification and random
access by vertex ID. But this implementation might be inefficient in
memory usage.

4) Fixed trivial bugs.

My next steps are:

 - Message Serialization.
 - Refactoring Queues and implement TODO things.
 - (Graph package) Performance Improvement.

Thanks.

-- 
Best Regards, Edward J. Yoon
@eddieyoon