Box delivered a bottom-line beat with expanding margins.Shares of enterprise content management software company Box (BOX 3.13%) rallied 15.7% this week through Thursday trading, according to data from S&P Global Market Intelligence.Box had earnings on Tuesday that came in ahead of expectations, along with a solid guide. While Box isn't posting eye-opening growth, it is doing a great job of expanding margins and prudently repurchasing stock.Box's growth is better than it seemsIn the second quarter, Box deli ...