feat(status): implement Hash for StatusCode

Change hash implementation to just use `derive(Hash)`

Author: Håvar Nøvik

src/status.rs

@@ -1,7 +1,6 @@
 //! 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.
@@ -29,7 +28,7 @@ use std::hash::{Hash, Hasher};
 /// Registry](http://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml) which is
 /// the source for this enum (with one exception, 418 I'm a teapot, which is
 /// inexplicably not in the register).
-#[derive(Debug)]
+#[derive(Debug, Hash)]
 pub enum StatusCode {
     /// 100 Continue
     /// [[RFC7231, Section 6.2.1](https://tools.ietf.org/html/rfc7231#section-6.2.1)]
@@ -534,12 +533,6 @@ 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):