Adds protocol class option to act as a full graphite replacement. #19
Currently, blueflood-carbon-forwarder can only receive pickle metrics, which means you have to have carbon-relay (or something similar) relaying metrics to blueflood-carbon-forwarder via pickled data.
With this PR, we will have the option to choose between received pickled metrics and receiving raw text metrics. The raw text metrics are what graphite itself is receiving.
This means I won't need to run the intermediate graphite node in order to get metrics from hosts via diamond, scripts, etc. -- I can now send directly from diamond to blueflood via blueflood-carbon-forwarder when running with the MetricLineReceiver protocol (rather than pickled protocol).