add quick start section

Author: melode11

README.md

@@ -39,6 +39,58 @@ cmake
 5. Add `<your boost install folder>/lib` to library search path, add `boost.lib`(Win32) or `-lboost`(Other) link option.
 6. Include `sio_client.h` in your client code where you want to use it.
 
+## Quick start
+The APIs are similar with JS client.
+
+Connect to a server
+```C++
+sio::client h;
+h.connect("http://127.0.0.1:3000");
+```
+
+Emit a event
+```C++
+//emit text
+h.socket()->emit("add user", username);
+//emit binary
+char buf[100];
+h.socket()->emit("add user", std::make_shared<std::string>(&buf,100));
+//emit message object with lambda ack handler
+h.socket()->emit("add user", string_message::create(username), [&](message::ptr const& msg)
+{
+});
+```
+
+Bind a event
+```C++
+/**************** bind with function pointer ***************/
+void OnMessage(sio::event &)
+{
+    
+}
+
+h.socket()->on("new message", &OnMessage);
+/********************* bind with lambda ********************/
+h.socket()->on("login", [&](sio::event& ev)
+{
+    //handle login message
+    //post to UI thread if any UI updating.
+});
+
+/**************** bind with member function *****************/
+class MessageHandler
+{
+public:
+    void OnMessage(sio::event &);
+};
+MessageHandler mh;
+h.socket()->on("new message",std::bind( &MessageHandler::OnMessage,&mh,std::placeholders::_1));
+```
+Send to other namespace
+```C++
+h.socket("/chat")->emit("add user", username);
+```
+
 ## API
 ### *Overview*
 There're just 3 roles in this library - `socket`,`client` and `message`.