Evaluate “rustwide”

[tarcieri]

Uses a restricted Docker container for performing Rust builds:

https://github.com/rust-lang/rustwide

May be helpful for (or eliminate the need for) this project.

[tarcieri]

I pushed up my WIP of a rustwide-based sandbox. It doesn't seem like there's an easy way to copy a development source tree into a container:

#7 (should've done a draft PR, oops)

In that regard, cargo-wharf (#6) might be a better fit for this project.