https://mma.prnewswire.com/media/454766/RM_LAW_PC_Logo.jpg?p=captionBERWYN, Pa., April 27, 2018 /PRNewswire/ — RM LAW, P.C. announces that a class action lawsuit has been filed on behalf of all persons or entities that purchased Gridsum Holding Inc. (NASDAQ: GSUM) (“Gridsum” or the “Company”) publicly traded securities between April 27, 2017 and April…