As of Friday’s close, Tesla (TSLA) is up more than 35% year-to-date, and up more than 370% over the last year. Would you bet against it? A lot of people are. Research firm Markit said the electric-car maker was the most shorted stock on the Nasdaq 100 (^NDX) in the last month. This is amid an increase in short-selling by 10% year-to-date on the Nasdaq Composite