feat(status): implement Hash for StatusCode

Implment the `Hash` trait for the `StatusCode` enum.

src/status.rs

@@ -1,6 +1,7 @@
 //! HTTP status codes
 use std::fmt;
 use std::cmp::Ordering;
+use std::hash::{Hash, Hasher};
 
 // shamelessly lifted from Teepee. I tried a few schemes, this really
 // does seem like the best. Improved scheme to support arbitrary status codes.
@@ -533,6 +534,12 @@ impl Ord for StatusCode {
     }
 }
 
+impl Hash for StatusCode {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.to_u16().hash(state);
+    }
+}
+
 /// The class of an HTTP `status-code`.
 ///
 /// [RFC 7231, section 6 (Response Status Codes)](https://tools.ietf.org/html/rfc7231#section-6):