Update SCEditor [size] tag to work with percentages.

gistfile1.js

$.sceditorBBCodePlugin.bbcode.set('size', {
        format: function($elm, content) {
                var size = $elm.data('scefontsize');

                if(!size)
                {
                        size = $elm.css('fontSize').replace("px", "") - 0;
                        
                        if(!this.baseFontSizePx)
                                this.baseFontSizePx = $elm.parents('body').css('fontSize').replace("px", "") - 0;
                        
                        size = Math.round((size / this.baseFontSizePx) * 100);
                }
                
                return '[size=' + size + ']' + content + '[/size]';
        },
        html: function(token, attrs, content) {
                return '<span data-scefontsize="' + (~~attrs.defaultattr) + '" style="font-size:' + (~~attrs.defaultattr) + '%">' + content + '</span>';
        }
});