Clear clippy warnings

Clear all the clippy warnings introduce by a recent clippy update.

src/client.rs

@@ -132,7 +132,7 @@ impl Client {
         let id = request.id.clone();
 
         let response = self.send_request(request)?;
-        if response.jsonrpc != None && response.jsonrpc != Some(From::from("2.0")) {
+        if response.jsonrpc.is_some() && response.jsonrpc != Some(From::from("2.0")) {
             return Err(Error::VersionMismatch);
         }
         if response.id != id {

src/simple_http.rs

@@ -479,7 +479,7 @@ mod tests {
             "http://me:weak@localhost:22/wallet",
         ];
         for u in &urls {
-            let tp = Builder::new().url(*u).unwrap().build();
+            let tp = Builder::new().url(u).unwrap().build();
             assert_eq!(tp.addr, addr);
         }
 
@@ -506,7 +506,7 @@ mod tests {
         ];
         for u in &valid_urls {
             let (addr, path) = check_url(u).unwrap();
-            let builder = Builder::new().url(*u).unwrap_or_else(|_| panic!("error for: {}", u));
+            let builder = Builder::new().url(u).unwrap_or_else(|_| panic!("error for: {}", u));
             assert_eq!(builder.tp.addr, addr);
             assert_eq!(builder.tp.path, path);
             assert_eq!(builder.tp.timeout, Duration::from_secs(15));
@@ -523,7 +523,7 @@ mod tests {
             // NB somehow, Rust's IpAddr accepts "127.0.0" and adds the extra 0..
         ];
         for u in &invalid_urls {
-            if let Ok(b) = Builder::new().url(*u) {
+            if let Ok(b) = Builder::new().url(u) {
                 let tp = b.build();
                 panic!("expected error for url {}, got {:?}", u, tp);
             }

src/simple_tcp.rs

@@ -85,7 +85,7 @@ impl TcpTransport {
     where
         R: for<'a> serde::de::Deserialize<'a>,
     {
-        let mut sock = net::TcpStream::connect(&self.addr)?;
+        let mut sock = net::TcpStream::connect(self.addr)?;
         sock.set_read_timeout(self.timeout)?;
         sock.set_write_timeout(self.timeout)?;
 
@@ -129,7 +129,7 @@ mod tests {
     fn sanity_check_tcp_transport() {
         let addr: net::SocketAddr =
             net::SocketAddrV4::new(net::Ipv4Addr::new(127, 0, 0, 1), 0).into();
-        let server = net::TcpListener::bind(&addr).unwrap();
+        let server = net::TcpListener::bind(addr).unwrap();
         let addr = server.local_addr().unwrap();
         let dummy_req = Request {
             method: "arandommethod",