Update SyntaxHighlighter 2.1.382 -> 3.0.83

The latest version of SyntaxHighlighter comes with some neat features but most importantly, you can select code without line numbers which makes copying code a breeze!

http://alexgorbatchev.com/SyntaxHighlighter/whatsnew.html

Updated the previous theme (shThemeRDark).
Removed unneeded SyntaxHighlighter image assets