Rewritten to use a url parameter for a conn string

URLs are pretty standard practice for most of the
cloud hosting providers out there that offer
mongo hosting, so we should keep parity.

Unfortunately, most of the driver had to be rewritten
to account for the differences in the MongoClient
driver that works with urls.
Merge pull request #2 from tedkulp/url-changes

Rewritten to use a url parameter for a conn string
Update README.md