micro-http: added MethodNotAllow status code

When server returns `Method Not Allow` responses,
it can attach to the response a HTTP `Allow` header.
Added support for HTTP response `Allow` header as
well.

Signed-off-by: Iulian Barbu <iul@amazon.com>
Signed-off-by: YUAN LYU <lyuyuan92@gmail.com>

src/common/mod.rs

@@ -142,7 +142,7 @@ impl Body {
 }
 
 /// Supported HTTP Methods.
-#[derive(Clone, Copy, Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub enum Method {
     /// GET Method.
     Get,