SHAWN MCFARLAND The Dallas Morning News ARLINGTON, Texas — Here are three takeaways from the Rangers’ three-game series sweep of the Seattle Mariners, capped off by Sunday’s 9-8 win. They retook first place in convincing fashion The Rangers began the weekend series vs. Seattle a half-game behind the Houston Astros in the AL West standings. They ended it with a twoand- a-half game lead, their…