Americans are feeling despondent about gas. It's a dour time for consumers — in April, the University of Michigan's Consumer Sentiment Index, which surveys consumers on how they feel about current and future economic conditions, hit an all-time low . It turns out that one small (or not-so-small) number has a lot of sway over how Americans feel about the economy: Gas prices. In recent years, there's been a pretty solid relationship between gas prices and consumer sentiment: When it's more