Fluor has a hidden gem inside, but is that enough to make it worth buying?Fluor (FLR +5.22%) is working diligently to make its business a more reliable source of cash flow. It has made significant progress as well. That's good news, but is it enough to justify buying the stock in the hope of setting yourself up for life? What if you add in Fluor's large ownership stake in an exciting nuclear power start-up?There's a lot to like about Fluor, but you still might want to tread with caution. Here's why.What doe ...