change fail icon to a red X, use yellow triangle for failed groups

You guys are using a yellow triangle to denote a failed test. But the problem is, you also use this yellow triangle for the groups/categories as well. This misleads the user as to how many tests actually failed. When you run the Example.ahk file, a quick glace at the gui might lead you to think there are 5 failed tests, when in fact there are only 2:

![Imgur](http://i.imgur.com/uv5MhiQ.png)

I've made a change to show the failed tests as a Red X, and left the failed groups as the yellow exclamation. This allows you to easily see the difference:

![Imgur](http://i.imgur.com/FqAjKt1.png)