Nearly 100 years ago, a woman peered into a boy's lunch box and saw a biscuit so bad it changed American baking forever.That moment and the product it inspired is the origin story of JIFFY Mix, the iconic "little blue box" made by Chelsea Milling Company in Chelsea, Michigan, about 15 miles west of Ann Arbor. Today, JIFFY's corn muffin mix is the No. 1 dry grocery item in the country, and the company's products are sold around the world. JIFFY M…