Remove Jekyll's default about page
Adjust title and description
Cleanup Jekyll config
Set proper url in Jekyll config
Exclude README from building
Add jekyll setup instructions to README
Remove SCSS as GitHub Pages still doesn't support it.

Reason: We want to make contributing as easy and conflictfree as
possible and there is the chance of people editing the CSS and not the
SCSS which would lead to conflicts as soon as someone else edits the
SCSS again.

Pull request for GitHub support: https://github.com/github/pages-gem/pull/75

/cc @verpixelt & @Dangoo