Thirty-four years after the last D.C. baseball team slunk out of town, the Washington Nationals play their first-ever home game against the Arizona Diamondbacks at 7:00 p.m. (TV: UPN 20). As if that isn’t exciting enough, the Nats arrive with a stadium-warming surprise gift: a winning record (5-4) and a two-game win streak (all road games, no less (of course)). It’ll be no small task to keep those winning ways going: The Diamondbacks, even shorn…