Just a little space can yield leafy results.Credit: Getty Images / YarphotoA big salad is the easy way to fix dinner in the summer, but buying endless heads of lettuce at the grocery store gets pricey, especially when growing your own harvest at home is practically foolproof. And while growing lettuce might bring to mind visions of long rows sitting neatly in an idyllic kitchen garden, you can also grow your own lettuce in containers.Whether you…