Investors with a lot of money to spend have taken a bullish stance on Pinterest (NYSE:PINS). And retail traders should know. We noticed this today when the positions showed up on publicly available options history that we track here at Benzinga. Whether these are institutions or just wealthy individuals, we don’t know. But when something this big happens with PINS, it often means somebody knows something is about to happen. Today, Benzinga’s options scanner spotted 13 options trades for Pinterest. This isn’t normal. The overall sentiment of these big-money traders is split between 76% bullish …