Updates to scan/kss-php v0.2.0

Updates scan/kss-php from v0.1.0 to v0.2.0. Modifies buttons.css to
use inline markup for providing an html example. Removes passing html
variable iniation in styleguide.html.twig. Updates block.html.twig
to set html from $section->getMarkup() if html was not passed into
the template.

Updates readme file to account for the above changes.