Investing isn’t just for the wealthy. A crop of services make it easy for savers to plant small amounts of money — like that fiver you found in the couch cushions — in the stock market. Microinvestment apps like Acorns, Stash and Robinhood allow would-be Warren Buffetts to bypass brokerage account minimums and skip the... Dayana Yochim is a writer at NerdWallet.