Jekyll 4.x.x support

• Support for Jekyll 4.x.x

Full Changelog: 1.0.1...3.00

Jekyll 3.x.x and GitHub Pages support

• Support for Jekyll 3.x.x
• Support for GitHub Pages - can be used as theme for GitHub pages; push repo to gh-pages branch
• Added gems required by Jekyll 3.x.x

Version 1 - Compatible with Jekyll 2.x.x

1.0.0

updated css url