function cssObjectToString (obj) {
		var res = [];
		for (var prop in obj) {
			if (obj.hasOwnProperty(prop)) {
				res.push(prop + ': ' + obj[prop] + ';');
			}
		}
		return res.join('');
	}
serialize an object into a string of CSS to use for style.cssText
@param {Object} obj
@returns {String}