Fix clippy warnings (#31)

src/redis.rs

@@ -43,7 +43,7 @@ impl RedisActor {
         Supervisor::start(|_| RedisActor {
             addr,
             cell: None,
-            backoff: backoff,
+            backoff,
             queue: VecDeque::new(),
         })
     }

src/session.rs

@@ -364,7 +364,7 @@ impl Inner {
         cookie.set_expires(time::now() - Duration::days(365));
 
         let val = HeaderValue::from_str(&cookie.to_string())
-            .map_err(|err| error::ErrorInternalServerError(err))?;
+            .map_err(error::ErrorInternalServerError)?;
         res.headers_mut().append(header::SET_COOKIE, val);
 
         Ok(())