added clarification to docs regarding middleware processing sequence, added delete method to TestRequest (#799)

* added clarification to docs regarding middleware processing sequnce

* added delete method to TestRequest, doc, and test

src/app.rs

@@ -301,7 +301,15 @@ where
     /// lifecycle (request -> response), modifying request/response as
     /// necessary, across all requests managed by the *Application*.
     ///
-    /// Use middleware when you need to read or modify *every* request or response in some way.
+    /// Use middleware when you need to read or modify *every* request or 
+    /// response in some way.
+    ///
+    /// Notice that the keyword for registering middleware is `wrap`. As you 
+    /// register middleware using `wrap` in the App builder,  imagine wrapping
+    /// layers around an inner App.  The first middleware layer exposed to a
+    /// Request is the outermost layer-- the *last* registered in
+    /// the builder chain.  Consequently, the *first* middleware registered 
+    /// in the builder chain is the *last* to execute during request processing.
     ///
     /// ```rust
     /// use actix_service::Service;

src/test.rs

@@ -386,6 +386,11 @@ impl TestRequest {
         TestRequest::default().method(Method::PATCH)
     }
 
+    /// Create TestRequest and set method to `Method::DELETE`
+    pub fn delete() -> TestRequest {
+        TestRequest::default().method(Method::DELETE)
+    }
+
     /// Set HTTP version of this request
     pub fn version(mut self, ver: Version) -> Self {
         self.req.version(ver);
@@ -549,7 +554,8 @@ mod tests {
             App::new().service(
                 web::resource("/index.html")
                     .route(web::put().to(|| HttpResponse::Ok().body("put!")))
-                    .route(web::patch().to(|| HttpResponse::Ok().body("patch!"))),
+                    .route(web::patch().to(|| HttpResponse::Ok().body("patch!")))
+                    .route(web::delete().to(|| HttpResponse::Ok().body("delete!")))
             ),
         );
 
@@ -568,6 +574,12 @@ mod tests {
 
         let result = read_response(&mut app, patch_req);
         assert_eq!(result, Bytes::from_static(b"patch!"));
+
+        let delete_req = TestRequest::delete()
+            .uri("/index.html")
+            .to_request();
+        let result = read_response(&mut app, delete_req);
+        assert_eq!(result, Bytes::from_static(b"delete!"));
     }
 
     #[test]