Fintech is making an interesting transition — from disrupting big banks to disrupting the disruptors. Companies like Robinhood, Lemonade and Credit Karma grew by addressing consumer needs that banks had ignored. Now a new generation of fintech companies is emerging. And they say their solutions are even better. One of them is Guac. It helps ordinary folks “save as they spend.” Our Andy Gordon and KingsCrowd founder Chris Lustrino sat down with Guac’s father/son team to discuss their…