/*!
 * get children of a parent element by tag name
 * gist.github.com/englishextra/d4789c5d30f6f6b429fdf7aaebeda7b1
 * based on gist.github.com/mgechev/5fbeca3627fef7bad0de
 */
function getChildrenByTag(root, tagName) {
	tagName = tagName.toUpperCase();
	root = root || document;
	var stack = [root],
	result = [],
	current,
	node;
	while (stack.length) {
		current = stack.pop();
		for (var i = 0; i < current.children.length; i += 1) {
			node = current.children[i];
			if (node.tagName.toUpperCase() === tagName) {
				result.push(node);
			}
			stack.push(node);
		}
	}
	return result;
}