Include Sass gem for scss.
Add gridster javascript and stylesheet.

In a separate commit so I don't accidentally roll it back.  Working on a
'playground' page so I can figure out how this thing works.
Temporary gridster playground.

Somewhere where I can screw around with this thing without the added
complication of Ember.
Don't orphan slides on board deletion.
Retool the board show page to reflect slide status.

This will serve as a place to tell people what to do next, or redirect
to the first slide is any exist.

Of course there seems to be a new bug with the way the slides
association in ember works when a board gets created while the app is
running.  I don't think it's my fault, either.  Meh.
PerspectiveAssignments basic output on slide.

That controller ain't great.  The output is not in any kind of grid
form, but that's coming up...