delete serving index.html (#802)

paddlehub/serving/app_single.py

@@ -318,7 +318,9 @@ def create_app(init_flag=False, configs=None):
 
     @app_instance.route("/", methods=["GET", "POST"])
     def index():
-        return render_template("main.html")
+        return '暂不提供可视化界面，请直接使用脚本进行请求。<br/>No visual ' \
+               'interface is provided for the time being, please use the' \
+               ' python script to make a request directly.'
 
     @app_instance.before_request
     def before_request():