Investors looking to create a seven-figure portfolio should probably own a diversified list of stocks. While capital growth should be a key focus, there's also a place for high-yield investments in the mix. But should 6.8%-yielding Kinder Morgan (KMI 1.02%) be on your buy list? There's a good reason to believe that this midstream giant won't be a millionaire maker anytime soon. And the dividend history here suggests that those considering buying it might be better off elsewhere.What does Kinder Morgan do?Si ...