Add Sass to Gemfile

It looks like I forgot to add this to the Gemfile and when running the
`jekyll` command without the `bundle exec` prefix the Sass conversion
was still working as it was already installed.
Update to the latest version of rack-jekyll

This version has yet to be pushed out to Rubygems.org.
Remove .rvmrc
Use Font Awesome!
Add hover state to social links

Also changed email and Twitter urls
Jekyll site update
Merge branch 'font-awesome'