Update blueflood graphite finder with rudimentary support for preagg

Preaggregated metrics have different default attributes than regular
metrics. A more comprehensive solution will need to be devised that
exposes these different values that blueflood calculates. For now, this
change will allow users to graph metrics sent into blueflood using
statsd.
Merge pull request #389 from dlobue/graphite_finder_support_preaggregated_metrics

Update blueflood graphite finder with rudimentary support for preagg