"Changed in version 3.0" section in PyMongo 3.0+ API documentation

As there's a behavioral change in the mongo_client module for 3.0 in which the MongoClient object will not validate a connection before performing an operation I think it may be a good idea to add the "Changed in version 3.0" section before the section quoted below.

The host parameter can be a full mongodb URI, in addition to a simple hostname.