Fix typo

Fix typo in test/test_echo_server.rs
diff --git a/test/test_echo_server.rs b/test/test_echo_server.rs
index 787269a..44830eb 100644
--- a/test/test_echo_server.rs
+++ b/test/test_echo_server.rs
@@ -88,7 +88,7 @@
         let sock = self.sock.accept().unwrap().unwrap();
         let conn = EchoConn::new(sock,);
         let tok = self.conns.insert(conn)
-            .ok().expect("could not add connectiont o slab");
+            .ok().expect("could not add connection to slab");
 
         // Register the connection
         self.conns[tok].token = Some(tok);