add syntaxhighlighter v2 & tinymce v4
1.add syntaxhl plugin to tinymce
2.modify preview plugin to support code syntax high light preview
modify syntaxhl plugin, support SyntaxHighlight options now.
default options is (SyntaxHighlighter.defaults):
auto-links: true
class-name: ""
collapse: false
first-line: 1
gutter: true
highlight: null
html-script: false
light: false
pad-line-numbers: true
smart-tabs: true
tab-size: 4
toolbar: true
wrap-lines: true