The Rust Project needs much better visibility into important metrics

OK, initial version is live at (ping @brson @alexcrichton). @ubsan suggested on IRC to make the grid of nightly release builds link to the relevant CI build pages, so I opened a GitHub issue.

Need to enable HTTPS soon, and then I’ll carve out some time to make the date range selectable after the initial page load. After that, I’ll start tackling other data sources and visualizations for them.