Script Summary: Sets email subject and snippet tooltips.
Sets "title" attributes on header items so email subject and snippet tooltips show on hover.
When the browser window is too narrow, part of the email header in the list view can get cut off. This script provides allows you to see what the whole subject is in the tooltip popup.
This can be helpful if you use the Multiple Inboxes feature with two columns.
20100228 - Simplified code
Changed tooltip to include both the title and snippet text so
everything can be seen at once when hovering.