write less-compiled css file to jupyter_customcss in jupyter_dir

def less_to_css(style_less):
    """ write less-compiled css file to jupyter_customcss in jupyter_dir
    """
    with fileOpen(tempfile, 'w') as f:
            f.write(style_less)
    os.chdir(package_dir)
    style_css = lesscpy.compile(tempfile)
    style_css += '\n\n'
    return style_css