changed sickle.xml so that output format is taken from input format
changed sickle.xml so that output format is taken from input format

MullinsLab/sickle,jdidion/sickle,ucdavis-bioinformatics/sickle,MullinsLab/sickle,najoshi/sickle,FabianFrancoRoldan/sickle,kdmurray91/sickle,biorelated/sickle,MullinsLab/sickle