New test type: Plaintext with pipelining

[bhauer]

I'd like to make implementation of a plaintext test a priority for Round 6. This should be less implementation effort than other recent tests so I think it's a nice simple target.

This issue is for drafting up the requirements. Please add any thoughts you have.

Tentatively, I am hearing the following ideas:

1. Response with just "Hello, World!"; no need to increase the response size dramatically.
2. Response should set content-type to text/plain.
3. Enable pipelining support in Wrk [1].
4. Dream that someone will donate 10 gigabit Ethernet hardware. It's safe to dream, right?

[1] wg/wrk#27

[bhauer]

This is now Test 6 and is documented at the results site: http://www.techempower.com/benchmarks/#section=code