scss support, create bower package

[lpaulger]

I used your library in my cribbage game https://github.com/lpaulger/cribbage-the-game and I wanted to contribute my changes to this library to the official package. Below are my changes, please review them.
I also thought it would be awesome to add this package to bower, so users can install straight from the bower package manager. I've included the bower.json configuration file (please review) and if its ok, then the only thing left to do is register the package on bower (http://bower.io/docs/creating-packages/#register). I really appreciate your effort on this lib :)

Changes:

• added support to add class to card '.selected' which will also
  increate the bottom distance.
• created scss support with configuration at the top
• created bower package so that css-playing-cards can be found on bower.
  Just need to register the package here
  http://bower.io/docs/creating-packages/#register

[selfthinker]

Thanks, this sounds generally good.
Sorry, I don't have much time at the moment. I will look at your changes within the next month or so...

[lpaulger]

I appreciate it. I'm really glad I found your project, it was very useful and a pleasure to work with. Since I extended it a bit with sass, and for use on mobile; I figured it would be nice to contribute those changes back.

I will compare the outputs of the scss file and compare it against the existing cards.css to identify any differences, I'm thinking that will make it easier to review my additions.