fancy demo design
use mezzanine for the demo homepage
FIX: widgy.py was clashing with widgy package
Remove unused import
Add the templates for the demo menu
Remove unneeded bootstrap assets
Remove duplicate manage.py
Overhauled the models for the demo project.

I deleted all of the silly example models and wrote out a realistic
HomeLayout with a Slideshow and Box widgets.  This commit also throws
away the migrations that we used to have in the demo project, which is
ok, because it's a demo project.
Use the menus that widgy_mezzanine provides.

I decided to use the menus that widgy_mezzanine provides (dropdown.html
and leftnav.html) instead of providing the demo projects own menus.  I
felt that those templates were very similar to the built-ins and were
just a distraction.
Add metadata block to demo/base.html
Added the pages/index.html for HomeLayout in demo.
Move demo_widgets templates to demo_widgets app.