Configure Windows CI through AppVeyor

[randomPoison]

Appveyor provides free online builds for open source projects so we should configure this project to use it for automating builds. Since Gunship is pure Rust this should be pretty simple. The build script should do the following:

1. Download the latest Rust nightly (assuming Appveyor doesn't have built-in Rust support the way Travis does).
2. Execute cargo build at the root of the project to build Gunship and all of its dependencies.
3. Execute cargo build --example for each of the examples.
4. Execute cargo test to build and run the tests.

Extra special bonus points if you also run all tests and examples for all of the crates in lib/.

The Appveyor website has documentation on how to setup builds so that should be the first place you look. I've also setup Appveyor for other projects so I might be able to offer some help.