HTTP router

[Thomasdezeeuw]

To route HTTP request based on the method and URL to the correct Service (#491).

impl Route {
    fn route<S>(&mut self, method: Method, url: &str, service: S) {
        // ...
    }

    fn get<S>(&mut self, url: &str, service: S) {
        self.route(Method::Get, url, service)
    }
}

Two additional useful features:

• Wildcards, e.g. /static_files/* would route any URL that starts with /static_files/ to a service.
• URL parameters, e.g. /user/{handle} would extract handle from the URL.

Possible data structure: https://en.wikipedia.org/wiki/Trie.

Blocked on #491.

[Thomasdezeeuw]

Pr #507 added the route! macro, but I'm leaving this open for a dynamic implementation.