Add Cargo, Webrender, Ripgrep

[Mark-Simulacrum]

Incrementally adding a smaller portion of the benchmarks listed in #192 to see
if we can afford to do this on current hardware.

cc @michaelwoerister

[Mark-Simulacrum]

We should also find some way long-term to do this without ~200,000 line additions, but that's a different problem we can solve later.

[nnethercote]

When I try to benchmark or profile cargo locally I get this error:

stderr=error: extra arguments to `rustc` can only be passed to one target, consider filtering
the package by passing e.g. `--lib` or `--bin NAME` to specify a single target

A normal cargo build in the cargo directory works, though.

[michaelwoerister]

Thanks @Mark-Simulacrum!

[nnethercote]

I updated my rustc and the cargo benchmark is now working.

[nnethercote]

Looking at http://perf.rust-lang.org, ripgrep is showing up on both the graphs page and the compare page, but cargo and webrender are not.

[Mark-Simulacrum]

I think they should start showing up soon -- I just pushed a fix for webrender (and deployed), Cargo was also somewhat recently fixed. I'll try to keep an eye on them.