Refactor the CSS to use SASS/SCSS

I have moved the original CSS file to solidare-it.scss, then did some
refactorings to leverage some of the benefits of SCSS. In particular
I seperated the color palette definition from its use.

Note that even though I have included the CSS file that is now generated by
SASS, it should never be directly edited!

To install SASS, given you have Rubygems available is simply

  gem install sass

To then generate the CSS from the source file, use

  sass solidare-it.scss:solidare-it.css
Remove tabs
Added a README for the CSS/SCSS stuff
Merge pull request #1 from plexus/introduce-scss

Introduce scss