https://medium.com/@adenforshaw/could-you-tip-your-driver-for-free-by-watching-ads-while-you-ride-maybe-even-get-the-ride-free-b83798c22d68#.ypp2vjvh7
https://medium.com/@adenforshaw/could-you-tip-your-driver-for-free-by-watching-ads-while-you-ride-maybe-even-get-the-ride-free-b83798c22d68#.ypp2vjvh7