Use trait objects and dynamic dispatch to abstract over NetworkStream

Server and client benchmarks show that this makes very little difference
in performance and using dynamic dispatch here is significantly more ergonomic.

This also bounds NetworkStream with Send to prevent incorrect implementations.

Allows the implementation of mock streams for testing and flexibility.

Fixes #5

src/server/mod.rs

@@ -6,7 +6,7 @@ pub use self::request::Request;
 pub use self::response::{Response, Fresh, Streaming};
 
 use net::{NetworkListener, NetworkAcceptor, NetworkStream};
-use net::{HttpListener, HttpAcceptor};
+use net::HttpListener;
 
 pub mod request;
 pub mod response;
@@ -31,7 +31,6 @@ impl Server<HttpListener> {
 }
 
 impl<L: NetworkListener<S, A>, S: NetworkStream, A: NetworkAcceptor<S>> Server<L> {
-
     /// Creates a server that can listen for and handle `NetworkStreams`.
     pub fn new(ip: IpAddr, port: Port) -> Server<L> {
         Server {
@@ -40,9 +39,8 @@ impl<L: NetworkListener<S, A>, S: NetworkStream, A: NetworkAcceptor<S>> Server<L
         }
     }
 
-
     /// Binds to a socket, and starts handling connections.
-    pub fn listen<H: Handler<A, S> + 'static>(self, handler: H) -> IoResult<Listening<A>> {
+    pub fn listen<H: Handler<A, S>>(self, handler: H) -> IoResult<Listening<A>> {
         let mut listener: L = try!(NetworkListener::bind(self.ip.to_string().as_slice(), self.port));
         let socket = try!(listener.socket_name());
         let acceptor = try!(listener.listen());
@@ -62,12 +60,12 @@ impl<L: NetworkListener<S, A>, S: NetworkStream, A: NetworkAcceptor<S>> Server<L
 
 /// An iterator over incoming connections, represented as pairs of
 /// hyper Requests and Responses.
-pub struct Incoming<'a, A: 'a = HttpAcceptor> {
+pub struct Incoming<'a, A: 'a> {
     from: IncomingConnections<'a, A>
 }
 
-impl<'a, A: NetworkAcceptor<S>, S: NetworkStream> Iterator<(Request<S>, Response<Fresh, S>)> for Incoming<'a, A> {
-    fn next(&mut self) -> Option<(Request<S>, Response<Fresh, S>)> {
+impl<'a, S: NetworkStream, A: NetworkAcceptor<S>> Iterator<(Request, Response<Fresh>)> for Incoming<'a, A> {
+    fn next(&mut self) -> Option<(Request, Response<Fresh>)> {
         for conn in self.from {
             match conn {
                 Ok(stream) => {
@@ -96,7 +94,7 @@ impl<'a, A: NetworkAcceptor<S>, S: NetworkStream> Iterator<(Request<S>, Response
 }
 
 /// A listening server, which can later be closed.
-pub struct Listening<A = HttpAcceptor> {
+pub struct Listening<A> {
     acceptor: A,
     /// The socket address that the server is bound to.
     pub socket_addr: SocketAddr,