Benchmark Tool - Enhancements - Round 1

First round of enhancements to the Logstash Benchmark Tool
- [ ] Add in some hardware stats to the output (Platform/CPU/Memory, etc) , to help contextualize the result if shared between people.
- [ ] Add a backgroud thread to add progress dots to let you know it is working, the apache test case takes a while and some feed back helps (kinda like M$'s progress bar, it means nothing, but makes you feel better).
- [ ] Add in an option for --testcase=custom and expose a --conifg-dir option such that, assuming I can figure out how to feed data in, I can use this for any test case.
- [ ] Add an option to store a csv file of the results, so that they can be source controlled, and graphed over time.
- [ ] Add in a clean command to clean up the $HOME/.logstash-benchmarks directory.

The above is not an exhaustive list (please add as needed), and is simply intended to be a place to gather thoughts for the next time someone has the time to invest in the Benchmark Tool.