Fix css plugin for IE7

[kate2753]

var style = document.createElement('style');
var useCssText = (style.styleSheet) ? true : false;
style.type = 'text/css';

results in useCssText = false in IE7 which is causing wrong logic to execute for attaching css styles.

var style = document.createElement('style');
style.type = 'text/css';
var useCssText = (style.styleSheet) ? true : false;

results in useCssText = true, hence moving up style.type assignment.

IE7 also throws 'Access denied' exception on

style.styleSheet.cssText = [style.styleSheet.cssText, text].join('\n');

It can not read value of the style.styleSheet.cssText, so replacing it with style.innerHTML.

I've checked value of style.innerHTML before and after adding styles using style.styleSheet.cssText. InnerHTML correctly reflects changes made via cssText so I think it should be a safe change.