Initial draft of benchmark suite (#120).

This is meant to allow us to assess the impact of a spec change on the performance of the algorithms via the reference implementation.

This initial draft contains a decent amount of dead code from abandoned ideas that will be cleaned up in the subsequent commit; however, I thought it'd be useful to have it in source control in case someone wants to use it later.
Remove dead benchmarking code.

There were ambitions of displaying nicely-formatted renderings of the params being tested, and thus code was included for that. But right now it's looking like that's not going to be that important, so remove it.
Add a recording-runner for the benchmark.

This records the results to a file on disk, so we can compare between snapshots.

While doing this, factored out the runner code to support both use cases.
Add something that diffs your recordings and shows the results
Add a README for the benchmarker