Can't change widget-title class

Hello,

i have installed your plugin in a website i am working on:

http://hachp.info.tm/newsite/

My problem is that i can’t manage to change the class for the titles of widgets so that different widgets have different title formats. My theme is “travelify” (http://colorawesomeness.com/themes/travelify/). Could you please tell me what to do?

Thanks in advance!

http://ww.wp.xz.cn/plugins/widget-css-classes/