Automate `sort-compress` program using `ni`

[spencertipping]

Compression trades speed for space, but we should be able to make that decision on the fly. There are two, perhaps three, action items here:

1. Trade space and speed more intelligently
2. Automatically prefer pigz to gzip, etc, if available
3. Rate-limit data throughput if we start running out of disk space, pause entirely if we're near critical so we don't crash the job