PyMongo should have *one* client class - MongoClient

MongoClient will support direct connection to mongod or mongos, replica set discovery and distributed reads, mongos high availablility (and possibly mongos load balancing).

The deprecated Connection and ReplicaSetConnection classes will be removed. MongoReplicaSetClient will be removed since MongoClient will provide the same behavior. (MongoReplicaSetClient may remain as a trivial subclass of MongoClient, to ease the transition.)

MasterSlaveConnection will also be removed. Users who still need MasterSlaveConnection can use PyMongo 2.x or implement something similar in their own applications (it's a very simple class).