Fallback to calling next route if no methods match (#224)

This removes a small foot gun from the routing.

This means matching different HTTP methods for the same route that
aren't defined together now works.

So `Router::new().route("/", get(...)).route("/", post(...))` now
accepts both `GET` and `POST`. Previously only `POST` would be accepted.

src/routing/or.rs

@@ -1,6 +1,6 @@
 //! [`Or`] used to combine two services into one.
 
-use super::{FromEmptyRouter, OrDepth};
+use super::FromEmptyRouter;
 use crate::body::BoxBody;
 use futures_util::ready;
 use http::{Request, Response};
@@ -45,12 +45,6 @@ where
     fn call(&mut self, mut req: Request<ReqBody>) -> Self::Future {
         let original_uri = req.uri().clone();
 
-        if let Some(count) = req.extensions_mut().get_mut::<OrDepth>() {
-            count.increment();
-        } else {
-            req.extensions_mut().insert(OrDepth::new());
-        }
-
         ResponseFuture {
             state: State::FirstFuture {
                 f: self.first.clone().oneshot(req),
@@ -119,18 +113,6 @@ where
 
                     *req.uri_mut() = this.original_uri.take().unwrap();
 
-                    let mut leaving_outermost_or = false;
-                    if let Some(depth) = req.extensions_mut().get_mut::<OrDepth>() {
-                        if depth == 1 {
-                            leaving_outermost_or = true;
-                        } else {
-                            depth.decrement();
-                        }
-                    }
-                    if leaving_outermost_or {
-                        req.extensions_mut().remove::<OrDepth>();
-                    }
-
                     let second = this.second.take().expect("future polled after completion");
 
                     State::SecondFuture {