Update eventEngine.py

事件引擎测试函数也去掉qt4，采用qtpy

vnpy/event/eventEngine.py

@@ -336,7 +336,7 @@ def test():
     """测试函数"""
     import sys
     from datetime import datetime
-    from PyQt4.QtCore import QCoreApplication
+    from qtpy.QtCore import QCoreApplication
     
     def simpletest(event):
         print(u'处理每秒触发的计时器事件：{}'.format(str(datetime.now())))
@@ -353,4 +353,4 @@ def test():
     
 # 直接运行脚本可以进行测试
 if __name__ == '__main__':
-    test()
+    test()