Updates to node-mongodb-native 3.3.3

[peterbroadhurst]

In order to pick up a fix for https://www.npmjs.com/advisories/1203 we wanted to update the mongodb version.

There were a couple of changes needed with the latest client:

• Needed to call db() to get the default DB object from the URI
  • http://mongodb.github.io/node-mongodb-native/3.1/api/MongoClient.html#db
• The close() needs to be on the client, not the db
• nextObject() has been renamed to next() on the cursor.
• We saw "op":"c" events ahead of the "op":"i"

[QuotableWater7]

@peterbroadhurst thanks for this PR! This driver upgrade fixes an issue I had with connecting to the oplog on a 3.6 Atlas cluster. The problem I ran into is my connection string would specify the local database but the connection would still go to the admin database and it tried to execute the oplog queries there 🤦‍♂. It seems the new mongo driver has fixed this issue and mongo-oplog correctly connects to local.

It would be 💯to get this merged soon so I don't have to point our package.json at a fork.