Fix README HTML styling. Copy CSS locally because it seems GitHub no longer serves up CSS.

Created a new directory in the dist folder: dist/css
Copied the stylesheets from @pmuir's github:

* https://github.com/pmuir/github-flavored-markdown/blob/gh-pages/shared/css/documentation.css
* https://github.com/pmuir/github-flavored-markdown/blob/gh-pages/shared/css/pygments.css