The Heidi ChroniclesBy: Wendy Wasserstein The graduating seniors of a Seven Sisters college, trying to decide whether to pattern themselves after Katharine Hepburn or Emily Dickinson. Two young women besieged by the demands of mothers, lovers, and careersnot to mention a highly persistent telephone answering machineas they struggle to have it all. A brilliant feminist art historian trying to keep her bearings and her sense of humor on the elevator ride from the radical