Vintner Chalone Spurns Rothchild,Stock Up  NEW YORK (Reuters) - The Chalone Wine Group Ltd. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=CHLN.O target=/stocks/quickinfo/fullquote"&gt;CHLN.O&lt;/A&gt; a  U.S. winemaker, on Monday rejected an existing buyout offer  from French luxury wine maker Domaines Barons de Rothschild,  saying it was now entertaining a better offer.