Fixed range patterns

I tried to build a project where rust-url was one of the dependencies and got many errors like this:

    Compiling url v0.1.0 (https://github.com/servo/rust-url#29f70a47)
    /Users/janapetrova/.cargo/git/checkouts/rust-url-1e22af4233079a1e/master/src/host.rs:189:34: 189:36 error: expected `=>`, found `..`
    /Users/janapetrova/.cargo/git/checkouts/rust-url-1e22af4233079a1e/master/src/host.rs:189                         c @ b'0' .. b'9' => c - b'0',

There was a PR is Rust not long ago, that breaks code: https://github.com/rust-lang/rust/pull/17584
So I changed range syntax to fix this problem.