adding mongodb.py
adding files to backends/mongodb
adding memcacheMongoReader.py
to settings.py, adding commented-out STORAGE_FINDERS line that would really go in local_settings.py if wanting to enable MongoDB finder.
adding .gitignore in /opt/graphite/conf dir to prevent complaints about graphite.wsgi file.
added thirdparty to gitignore, since don't want to commit this dir to repo.
added storage dir to .gitignore, since it should contain untracked files.