Improve benchmark script. Add [-n <reqursts>] and [-c <concurrent>] o…

[jkklee]

Improve benchmark script. Add [-n ] and [-c ] options, multi clients test use multi processes modle

[coveralls]

Coverage remained the same at 85.62% when pulling 2e21d14 on jkklee:unstable into a49d21a on Grokzen:unstable.

[Grokzen]

@jkklee There is alot of code that you have commented out that needs to be brought back, all the timeit code for example and alot of stuff that you improved and is not needed but was not removed, that needs to be cleaned up. I like where it is going and i would like to get it in, but you need to fix some cleanup before i can merge this.

[Grokzen]

A few other lines of cleanup you need to add is to update the docs in this section https://github.com/Grokzen/redis-py-cluster/blob/unstable/docs/benchmarks.rst

[jkklee]

@Grokzen done, please check it.

[Grokzen]

Some changes i require before i merge this. Looks good overall and i tested it locally and i am happy with the overall changes.

[jkklee]

@Grokzen sorry I'm not good at github's pull_requests