Depend on remove_dir_all 0.6

[dvtomas]

I'm removing duplicate dependencies from my project, and remove_dir_all 0.5 (tempfile) vs 0.6 (others) is one of them

[Stebalien]

Note: This is currently blocked because remove_all_dirs 0.6+ adds a dependency on rayon, and I'm strongly against having a temporary file library launch new threads.

[messense]

Is remove_dir_all still needed? Cargo recently removed it and std::fs::remove_dir_all shows better performance: rust-lang/cargo#11333

[Xaeroxe]

Resolved in #207. Also, remove_dir_all no longer requires rayon.

[stanislav-tkach]

By the way, there is a race condition in old (<0.8.0) versions of the remove_dir_all library, so it would be nice to either update or remove this crate.

[Xaeroxe]

Changed my mind, switched to removing it in #208

[adumbidiot]

Was rust-lang/rust#29497 worked around?