Add missing API docs

These were written without much knowledge of the actix-web internals!
Please review carefully!

src/server/mod.rs

@@ -111,6 +111,7 @@ pub struct ResumeServer;
 ///
 /// If server starts with `spawn()` method, then spawned thread get terminated.
 pub struct StopServer {
+    /// Whether to try and shut down gracefully
     pub graceful: bool,
 }
 

src/server/srv.rs

@@ -686,7 +686,7 @@ where
 {
     type Result = ();
 
-    fn handle(&mut self, msg: Conn<T>, _: &mut Context<Self>) -> Self::Result {
+    fn handle(&mut self, _msg: Conn<T>, _: &mut Context<Self>) -> Self::Result {
         unimplemented!();
         /*Arbiter::spawn(HttpChannel::new(
             Rc::clone(self.h.as_ref().unwrap()),