Allow prefix with SIMPLE_HOSTNAME

[Benedict Dodd]

Given this method: https://bitbucket.org/travis_bear/grinder_to_graphite/src/2ff018ff52eff60c3748a641fba959a183821d20/g2g/aggregator/non_http.py?at=master#cl-105

Could we have it so we can remove the host name? This has implications when using large numbers of agents, from AWS with dynamic IP/hostnames, and one wants to have longer retentions in Graphite. I.e. An excessive amount of storage is needed.

[Travis Bear]

This is a fair comment. Any chance of a pull request? If not, I'll throw it into my queue.