Add larger CPU benchmarks

[kburns]

I'd like to add tables benchmarking the codes on better CPUs, like those you'd find on nodes in standard university clusters, etc.

Something like a full node with 32 cores and a decent amount of memory would be a much more meaningful comparison to performance on a GPU, than timings on our laptop processors.

Happy to run this on the flatiron cluster, for instance, which has 48-core Skylake nodes.