(Reuters) -Car rental firm Hertz Global said on Tuesday it had launched a fully online car-buying marketplace, as it leans on the demand for used vehicles. The company's shares rose as much as 2.5% after the news. The announcement follows Hertz's collaboration with Amazon.com's automotive retail platform, Amazon Autos, to sell preowned vehicles. The company said it would also provide customers an option for trade-in offers. Hertz has been facing bumpy rental demand, which has prompted it to shed much o ...