MEXICO CITY, Sept 27 (Reuters) - The mayor of a small town in western Mexico was found on Monday stoned to death in the third attack on a public official in the country in less than a week, local authorities said. The bodies of Gustavo Sanchez, mayor of Tancitaro in Michoacan state, and an aide were found, officials said. "It appears they stoned them to death," a source from the local prosecutor's office said on condition of anonymity. Local media reported that the bodies were found in the back of a flat-bed truck. There was no immediate indication whether the...