gfm-syntaxhighlighter allows for syntax highlighting while using github flavored markdown
Plugins:
* wp-gfm
* syntaxhighlighter
Activate all three plugins, use wp-gfm as intented and enjoy.
Syntaxhighlighter Evolved comes with code hook attributes that can modify fenced in code blocks, the descriptions of each attribute is on the Syntaxhighlighter Evolved settings page.