The Girl Scouts of America may get credit for making the lowly marshmallow synonymous with campfires — and for discovering its raison d’être by smashing it between graham crackers with a mess of chocolate — but Maine has Colby grads and Brooklyn transplants Madison Gouzie and Eric Holstein to thank for elevating the humble s’more to an elegant confection that can be consumed without shame in broad daylight. The duo behind Portland’s new Marshmallow Cart peddles massive homema