cargo-mutants VS conserve

Hi Rusty!

For a later hack in the same vein, check out https://github.com/sourcefrog/cargo-mutants

cargo-mutants got a couple of releases over the weekend, fixing some environment-triggered bugs on Windows and Linux ecryptfs, and adding a better overall progress indicator (demo: https://asciinema.org/a/481375). It is getting better at avoiding uninteresting or pointless mutations, although there's a lot more to do there, and at printing function name paths well.

While working on Conserve and cargo-mutants I felt that existing Rust progress-bar libraries like Indicatif didn't give me enough control of how the bar was drawn, or at least I was working around them to insert my own text. For example, I wanted to draw several counters into a single line, and it seems like the only way to do that is to just push in a text string.

Continuing with some fast-follow enhancements in cargo-mutants in response to user feedback: for example doctests are typically slow and in some trees not important for coverage, so you can now skip them.

I got cargo-mutants to a state where I felt I could announce it and ask for public feedback.

While working on Conserve and cargo-mutants I felt that existing Rust progress-bar libraries like Indicatif didn't give me enough control of how the bar was drawn, or at least I was working around them to insert my own text. For example, I wanted to draw several counters into a single line, and it seems like the only way to do that is to just push in a text string.