Add benches

[cesarb]

No description provided.

[valarauca]

Going to have to deny this.

1. Benches are depreciated

2. This would make the crate nightly only again. I think if we're going to add nightly only features they should be placed behind a feature flag.

3. A better approach would be criterion but if we're adding that it should be behind a feature flag as somebody importing this likely won't want to download a benchmark crate to build this crate. Also graphs are nice

[cesarb]

This would make the crate nightly only again. I think if we're going to add nightly only features they should be placed behind a feature flag.

There's a trick to add benches without making a crate nightly-only, and without needing a feature flag. The benches/ directory is compiled only for cargo bench; if you put all your #[benches] code there, everything else (cargo test, cargo build, everyone who uses your crate as a dependency) keeps working on stable.

And that is exactly what I did. If for instance I use my distro's rustc 1.14.0 (which, of course, has no access to nightly features), cargo build and cargo test still work.

A better approach would be criterion but if we're adding that it should be behind a feature flag as somebody importing this likely won't want to download a benchmark crate to build this crate.

There's an easy solution for that too: use dev-dependencies instead of dependencies. The dev-dependencies are used only for tests and benches, not for someone importing the crate. See http://doc.crates.io/specifying-dependencies.html#development-dependencies for details.

Benches are depreciated

From what I understand, what we have there is just someone suggesting to deprecate benches, not benches being deprecated. But I see no problem using an alternative framework instead.