Test replication functionality

[furushchev]

• Use argument parser for replicator_client.py keeping back compatibility

  replicator_client.py now can takes some optional arguments:

  $ rosrun mongodb_store replicator_client.py
  usage: replicator_client.py [-h] [--move-before MOVE_BEFORE]
                              [--delete-after-move]
                              database collection [collection ...]

• Added test codes for replication

• Fixed some bugs to test replication

• Fixed for keeping compatibility between pymongo 2.X and 3.X