List divider and Zebra Stripes

* The border that separated the list-containter and the
archived-list-container looked a bit strange in the edge
after the latest changes. I changed it to a separate element
that solves it and makes it look a little bit better than the
original one.
* Removed the gradient that was there from JqueryUI and added
zebra stripes to the list items.
Changed width to look better
and changed a method name.
Updated from comments

New color on archived items
Updating stripes when archiveing
Zebra stripes on children

Added this.
Updated after last comment
Merge pull request #115 from nilsi/gradient_fix

List divider and Zebra Stripes