Add missing .

Author: jsor

README.md

@@ -3,7 +3,7 @@
 [![Build Status](https://travis-ci.org/reactphp/socket.svg?branch=master)](https://travis-ci.org/reactphp/socket)
 
 Async, streaming plaintext TCP/IP and secure TLS socket server and client
-connections for [ReactPHP](https://reactphp.org/)
+connections for [ReactPHP](https://reactphp.org/).
 
 The socket library provides re-usable interfaces for a socket-layer
 server and client based on the [`EventLoop`](https://github.com/reactphp/event-loop)