switched to using pymongo rather than REST interface
fixed up btree, lock to make it work with current format of serverstatus, removed problematic auth code temporarily
updated readme to reflect 2.4+ dependency and to note that auth support is pending
Added the document number graph
Merge pull request #1 from Cog-g/feature/add_documents_graph

Added the document number graph
add support for host, port, user and password configuration

- use MONGOURL env variable