Change Connected::connect_info to return Self (#396)

I've been thinking that having an associated type probably isn't
necessary. I imagine most users are either using `SocketAddr` to the
remote connection IP, or writing their own connection struct.

src/routing/mod.rs

@@ -429,9 +429,7 @@ impl<S> Router<S> {
     /// }
     ///
     /// impl Connected<&AddrStream> for MyConnectInfo {
-    ///     type ConnectInfo = MyConnectInfo;
-    ///
-    ///     fn connect_info(target: &AddrStream) -> Self::ConnectInfo {
+    ///     fn connect_info(target: &AddrStream) -> Self {
     ///         MyConnectInfo {
     ///             // ...
     ///         }