backwards-compatible to pymongo 2.1.1

Add backward-compatibility for pymongo-2.1.1, which is offered as an RPM on EL6 compiled with bson support and is easier to install on servers (for example, puppet has a yum provider but not a pip provider without writing your own).

Is there a better way of doing this or is it just going to have to be as ugly as I've made it? o.O