This commit fixes loads of crates (47!) had unused dependencies, or
mis-configured dependencies (test deps as normal deps).
I added the "unused_crate_dependencies" to all crates to help prevent
this mess from growing again!
https://doc.rust-lang.org/beta/nightly-rustc/rustc_lint_defs/builtin/static.UNUSED_CRATE_DEPENDENCIES.html
This has the minor downside of false-positives when specifying
dev-dependencies for test/bench binaries - these are files in /test or
/benches (not normal tests). This commit includes a workaround,
importing them in lib.rs (gated by a feature flag). I think the
trade-off of better dependency management is worth it!
Carol (Nichols || Goulding)
Dom Dwyer