* Tesla’s stock had its best single day of trading since May 2013. * The electric automaker turned in an unexpectedly profitable third-quarter and better than anticipated progress toward getting its Shanghai factory operational. * “Skeptics had legitimate concerns in the past, but Tesla is now building cash, winning market share, and boosting margins,” Piper Jaffray says. Tesla’s stock popped big when trading began on Thursday, after the electric automaker turned in an unexpectedly profitable third-quarter and better than anticipated progress toward getting its Shanghai factory operational. “Skeptics had legitimate concerns in the past, but Tesla is now building cash,...