Provide module that will expose Blueflood to graphite-web

The finder users the v2.0/metrics/search API to find metrics.
The reader reads metrics from an appropriate resolution and returns them.

http://graphite.readthedocs.org/en/latest/storage-backends.html

I don't have strong opinions about where this code lives. Maybe `contrib` is the right place.

I've include  a setup.py (mostly copied from the ceres finder), and a simple test. If I knew more about unittest it would be a better test.

This is a good start. I've personally tested this against graphite-web and a local grafana checkout. It works.
Should this be `TenantBluefloodFinder`?