In golf, they call it a mulligan. A do-over. There's no formal name for what President Obama and Chief Justice John G. Roberts Jr. did last night. After flubbing his one role on Inauguration Day -- administering the oath of office to Obama -- Roberts traveled to the White House to re-administer the oath. Just to make sure. "We decided it was so much fun . . .," Obama joked while sitting on a couch in the Map Room. Obama stood and walked over to make small talk with pool reporters as Roberts donned his black robe. "Are you ready...