function getNode (input) {
		if (input.tagName) {
			return input;
		} else if (toString(input) === '[object String]') {
			return document.querySelector(input);
		} else if (input.length) {
			return input[0];
		}
		return null;
	}
return a DOM Node matching variable input
input might be a DOMElement, a DOMCollection or a string
@param input
@returns DOMElement