README.md: Add syntax highlighting to python code (#723)

README.md

@@ -15,23 +15,25 @@ You can install this package as usual with pip:
 Example
 -------
 
-    from flask import Flask, render_template
-    from flask_socketio import SocketIO, emit
+```py
+from flask import Flask, render_template
+from flask_socketio import SocketIO, emit
 
-    app = Flask(__name__)
-    app.config['SECRET_KEY'] = 'secret!'
-    socketio = SocketIO(app)
-
-    @app.route('/')
-    def index():
-        return render_template('index.html')
-
-    @socketio.on('my event')
-    def test_message(message):
-        emit('my response', {'data': 'got it!'})
-
-    if __name__ == '__main__':
-        socketio.run(app)
+app = Flask(__name__)
+app.config['SECRET_KEY'] = 'secret!'
+socketio = SocketIO(app)
+
+@app.route('/')
+def index():
+    return render_template('index.html')
+
+@socketio.on('my event')
+def test_message(message):
+    emit('my response', {'data': 'got it!'})
+
+if __name__ == '__main__':
+    socketio.run(app)
+```
 
 Resources
 ---------