PyMongo compatibility

[AndrewCEmil]

To support older and newer versions of PyMongo, code that looks like this:

import pymongo
...
conn = pymongo.Connection(<options>)

should change to:

try:
    from pymongo import MongoClient as Connection
except ImportError:
    from pymongo import Connection
...
conn = Connection(<options>)

[tjj5036]

This was largely addressed in 215b1f2 although another commit has a fix where one import was neglected.