CNBC's Jim Cramer explained why he thinks newly-minted IPO Klarna is a buy even after shares climbed during its first trading session."While Klarna roared right out of the gate, the stock hasn't gone to an insane valuation yet. I think the numbers look good, so I think it can be bought at these levels," he said, with the caveat that overall, he prefers competitor Affirm.Klarna opened at $52 and saw gains on Wednesday after the the company priced its IPO above the expected range. The Swedish online lender is ...