Backlog: Use buttons instead of select for status

Redesign the status-change UI, making it more
prominent in the details panel, and more fun 
to change status by pressing buttons rather than
choosing from a menu.
Add YUI slider lib

We investigated using the YUI slider control
for changing status, but ending up not going
with it. We might use it for something else,
though, so we're keeping this lib file around
for now.
Refactor: Remove slider artifacts

Remove the artifacts from the latest status-change
design.
Refactor: Put archive init code in own function
Backlog: Remove button outlines

Also keep the save buttons white upon hover.
Fix: Backlog: Use links, not buttons for status

Using buttons for status updates affected the
default button situation with the form, which
meant that pressing enter no longer saved the 
story.
Fix: Remove design artifact
Backlog: Save stories when status changes

It feels like the state of the story should 
be saved when the status buttons are pressed,
so let's do that.
Backlog: Show a 'stop' icon when a story is sad
Fix: Hide status buttons in mileposts