Sen. Marco Rubio, R-Florida, on Friday defended his decision to skip a major vote in the Senate that afternoon to fund the government through September, and he took a swipe at a GOP rival who called on him to resign from Congress.In an interview with CBS News' Face the Nation host John Dickerson, Rubio was asked to respond to Sen. Rand Paul, R-Kentucky, who told Politico Friday that Rubio should resign from the Senate after missing the critical vote. "Look, I'm running for president," Rubio told Dickerson in Dubuque, Iowa ahead of his town hall. "We do our job everyday....