Adding Cascade Framework

Cascade Framework is a frontend framework focused on CSS, like Twitter
Bootstrap or Zurb Foundation.

Cascade Framework 1.x is written in pure CSS. It supports responsive
design and all modern browsers as well as IE6+. For an optimal balance
between footprint and flexibility, it implements a modifier design
pattern inspired by SMACCS and OOCSS.

In an article posted on October 13, 2013, Crunchify lists Cascade
Framework as #5 in its "Top 5 New and Favorite Responsive Frameworks".
The first four are respectively Bootstrap, Cardinal, TypePlate and
Furrato.

In an article posted on October 24, 2013, CodeGeekz lists it among "12
Fresh and Useful Frameworks". Other projects listed are Gumby, Solved by
Flexbox, UI Kit, SkelJS, Cardinal, Layers CSS, Grid Forms, Gridism,
Maxmert, Rocket CSS and Kube Framework.

Linux portal Linuxlinks lists Cascade Framework as one of the ten
"finest open source lightweight frameworks to kick start CSS and HTML
projects". Other projects listed are Quantum Framework, Pure, Baseline,
HTML KickStart, Base, KNACSS, Toast, Motherplate and HTML5 Boilerplate.

Cascade Framework was also Softpedia's Script of the day on September 6,
2013.

At the moment of this commit, Cascade Framework has 97 stars on its main
repo and 39 stars on its mirror repo.