Benchmark stdlib compression code

At PyConUS, I was chatting with @gpshead about adding compression benchmarks. While a lot of the "heavy lifting" of compression happens in the libraries CPython binds (zlib, liblzma, etc.), the handling of output buffers in CPython has a significant impact in performance, and is something we don't have a lot of visibility into the performance of.

One of the better known cross-algorithm compression benchmarks I'm aware of is lzbench, which tests compression performance of the Silesia compression corpus across many algorithms. I figure running compression benchmarks at varied settings on Silesia would provide a good starting point for benchmarking the output buffer and other binding code.

No files, tests, or entry points are named. Start by reviewing pyperformance's existing benchmark structure, then compare lzbench's Silesia methodology and the zlib/liblzma bindings to define varied settings and output-buffer measurements. Done means reproducible compression benchmarks that expose the CPython-side performance described in the issue.