Department of Statistical Science, Duke University, Durham, North Carolina, United States of America.|Program in Computational Biology and Bioinformatics, Duke University, Durham, North Carolina, United States of America.|Program in Computational Biology and Bioinformatics, Duke University, Durham, North Carolina, United States of America.|Department of Genetics, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.|Department of Computer Science, Center for Statistics and Machine Learning, Princeton University, Princeton, New Jersey, United States of America.