(Flickr photo of No. 54 metrobus at the Archives-Navy Mem’l-Penn Quarter station by FurCafe via DCist Photos) >> In case you’ve been living under a rock, today is opening day for the city’s new baseball team, the Washington Nationals. And WMATA says it’s ready to handle the crowds on metrorail. Rush-hour service will start at 3 p.m. and will run until the first pitch a little after 7 p.m. Expect the Blue and Orange…