Update Jekyll to latest stable version, 2.2

Update jekyll-assets to latest version for support of Jekyll 2.2
Remove use of rdiscount, kramdown works fine
Remove explicit SASS dependency, as Jekyll takes care of that now
Switch to using Rouge for syntax highlighting

Adjust highlighter used in post because Rouge doesn't have an Apache specific one
Update assets config syntax for newer settings
Merge pull request #1 from vincecima/update-jekyll-major-version

Update jekyll major version and fix any associated problems