Make Cargo build work on Windows

Using OSX, so this needs to be tested on Windows

See https://github.com/bjz/glfw-rs/issues/200
Merge pull request #204 from bvssvni/master

Make Cargo build work on Windows
Switch to cargo!
Use syntax extension to generate link arguments
Import `semver` crate using cargo
Simplify syntax extension implementation
Merge pull request #205 from bjz/cargo

Switch to cargo!
Fix missing `const`s in README.md.
Merge pull request #206 from metajack/fix-readme-const

Fix missing `const`s in README.md.