By Tom Verducci Nobody should be surprised that New York is getting plunked. Here are the facts behind all the April baseball gripes. Welcome to The Opener, where every weekday morning during the regular season you’ll get a fresh, topical column to start your day from one of SI.com’s MLB writers. The Mets are fighting mad. The baseballs are either dead, too slick, spending too much time in humidors or all of the above. The weather is too cold. It’s been a great month for conspiracy theorists but a lousy month for hitters. There has never been a time in MLB history with fewer hits in the averag…