Add beginning of concrete Foundation clone

We are building a clone of Foundation's stylesheets in Stylus (instead
fo Foundation's choice of SCSS/SASS).

This early version has only our own version of modular-scale. We are
basing some of our work off of Nibble.
Add Foundation default settings
Add convert-number-to-word function
Add grid-calc function
Add font-size mixin
Add more mixins from Foundation

We also renamed this framework "ground-floor" because "concrete" is
already taken by another Node package.
Add standard ratios
Add common styles and some component styles
Add topbar and navbar styles
Add media queries, UI and Orbit styles
Add tabs styles
Add clearing,joyride and reveal styles
Clear out old version of orbit styles
Add Foundation additions

These are our personal styles that we add on top of Foundation.
Clean out nibble
Add a fix for scaling videos in Orbit slides