Doc continuous integration

Rust is a fast-moving project and it can still be difficult for package maintainers to keep up with the Rust master branch. We recommend that maintainers use Travis CI to test their packages against Rust nightly builds and register with the Rust CI community dashboard. See the Rust CI page for further instructions.

First things first, you'll need to set up your project with Travis CI. Sign up for an account on their website, and then in Travis's profile page, make sure the project you want to check is enabled.

Next, you'll need a .travis.yml in the root of your project.

TODO: Finish this off.