Add shoadow to valid section.

Move shadow from navigation to all header.
Merge pull request #46 from vash000/layout-fixes

Add shadow to valid section.
Set none decoration for element link a
Merge branch 'link-a' into alpha
Create code club section slides
Merge pull request #48 from pgle/teach

Create code club section slides
Add close button for section slides
Merge pull request #49 from pgle/teach

Add close button for section slides