Evaluate using Failure for error handling

[ALSchwalm]

I would like to be better able to preserve context for errors. The failure crate seems like a good solution here, but I'm not sure how practical it is to use no_std (or if it really buys us much over just directly using our Error type).

[mehcode]

Consider using https://github.com/dtolnay/anyhow which provides only failure::Error and some sugar around that. It also supports no_std.

[ALSchwalm]

That looks like it might be a good fit. Thanks!