switch CSS to SCSS

Rename the files, ignore the genereated CSS files.
Add a README.
use SCSS nesting feature

Go over all stylesheets and use the SCSS selector nesting feature
to shorten code. Also, some coding style changes: empty line bet-
ween selector blocks and OTB style.
add mixins for CSS3 cross-browser properties
shorten cross-browser mixin
fix SCSS @import path
move markdown @import

Import it only where needed (currently candidates/view.scss),
and use SCSS import.
minor styling fix
use property nesting syntax
move global mixin file

An underscore before the file name prevents SASS from compiling
the file itself. It is still available as @import under the same
name as before.
Merge pull request #21 from maul-esel/SCSS

Switch to SCSS for stylesheets