Remove the rouge gem from the project

Remove the rouge gem from the project in favor of pygments.
Update jekyll to 2.2 and remove jekyll-import

Update jekyll to latest version 2.2 through the github-pages gem and
remove the jekyll-import gem as it will not be used anymore.
Remove the layout warning in the atom feed
Update the three css layouts
Change the favicon and the apple-touch-icon
ensure IE is running in latest rendering mode
Use the new sidebar-overlay
Change the baseurl and add emoji support
Merge branch 'albertogg/update-to-jekyll-2.2'