Streamline grunticon and cssmin workflow

Change folder names to start with _ to avoid being rebuilt by Harp
Use imagemin to copy over and auto-optimize the pngs
Add cssmin so I don't have to keep tweaking Codekit
Move .nav after .main in HTML source order as referenced in #4

.nav now goes after .main
Mustard-cutting browsers will move it back in place for mobile menu
animations. (knee-up is all absolute positioning so it doesn't matter
there)
Navburger button always visible
Remove .banner animations
Add .MEDIA-down class visibility
Initial commit of Technical Debt page