added iterator_split() function to IOTools
added iterator_split() function to IOTools

AntonioJBT/CGATPipeline_core,AntonioJBT/CGATPipeline_core,AntonioJBT/CGATPipeline_core,CGATOxford/CGATPipelines,AntonioJBT/CGATPipeline_core,CGATOxford/CGATPipelines,CGATOxford/CGATPipelines,CGATOxford/CGATPipelines,CGATOxford/CGATPipelines