Here's some potentially great news for Donald J. Trump. A key market barometer that shares the President-elect's initials has been rallying lately. And that's often a promising sign for the broader markets and economy. The Dow Jones Transportation Average (DJT) -- often referred to by traders as the DJT or the Dow Jones Transports -- is up more nearly 10% since the election and has continued to head higher so far in 2017. Why is that a positive for Trump? The DJT has 20 key airline, railroad, trucking and shipping stocks in it. American (AAL), United (UAL), Union Pacific (UNP),...