Forterra cofounders spent about 20 years developing technology to retrofit vehicles to drive themselves. Now the startup is cashing in, winning a $93 million contract from the U.S. Army. https://t.co/mwSqrXEZq8 (Photo: Shawn Hubbard for Forbes) #BillionDollarStartups https://t.co/XUDf8GWk1a