Adding helper to truncate event list-item 'output'.

This implements a naive and arbitrary truncation of the event 'output' attribute.  This creates a nice layout for the current even list-items, while the full output is still available in the modal.

Limiting to 90 characters seems about right.  And by that I mean that it fit perfectly on my laptop.

UPDATE:  Here is a CSS implementation that seems OK.  I guess I don't like hard-coded pixel heights, but this does the trick, and is more adaptable to different screen widths (Rather than the arbitrary character length).

What do you think?

```
td.output {
  line-height: 28px;
  height: 20px;
  overflow: hidden;
  display: block;
}
```