Bioinformatics and Research Computing, Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America. lewitter@wi.mit.edu|Bioinformatics and Research Computing, Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America. lewitter@wi.mit.edu|Bioinformatics and Research Computing, Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America. lewitter@wi.mit.edu|Bioinformatics and Research Computing, Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America. lewitter@wi.mit.edu