Unwrap pygmentize output if necessary

Hi,

using these changes the output of the `pygmentize` command will be unwrapped of the additional `div`, `pre` tags generated by the highlighter if you enable *wrapping* by specifying the `:unwrap => 0` parameter. This is especially useful if you want to use options like *line numbering*.

Example usage:

    filter :colorize_syntax,
        :default_colorizer => :pygmentize,
        :pygmentize => { :linenos => 'inline', :linenospecial => 5, :nowrap => 0 }

I am fairly new to ruby - so please bear with me in case the code style is not as desired :-)

Cheers,
Gregor