Sass: Added Sass versions of the default CSS files.

Also cleaned up some markup (removed duplicate IDs on the page by changing state elements to use classes instead); Cleaned up the included CSS by simplifying selectors and moving the contents out of the HTML file and into Sass/CSS files; Added an assets folder containing clearly delineated sass, font, and css folders; Updated the readme to reflect the changes.
Typo: Fixed typo in readme
Merge pull request #9 from jackieee/master

Added Sass versions of default CSS files