Implement proper benchmark suite.

[amcgregor]

• Pure non-interactive command-line, optionally with coloured output.
  • Useful when combined with Tox to gather stats across many Python runtimes.
• "Terminal GUI" operation with an urwid or similar curses interface for exploring the benchmarks:
  • Available engines in a list/table, with non-installed engines available for installation, but hidden.
  • Ability to view example template and code to render the template.
  • Sort, the usual. Export in a variety of formats and otherwise replicate the CLI options.
• Should probably be a separate package or tool. ;)