optimize easytier-web (#522)

1. use default compress level for tower_http. the best level consume
lots of memory
2. add more help message and command line arg.

easytier/src/utils.rs

@@ -168,4 +168,4 @@ mod tests {
         tokio::time::sleep(tokio::time::Duration::from_secs(1)).await;
         tracing::debug!("test display debug");
     }
-}
+}