Fix split-info-file to be able to specify an output directory

Need to be able to specify a parent directory where the split directory will be stored. If not specified, should default to the parent directory of the log file for now so they will be in the same place.

In conjunction with #17 (closed), it would be good to be able to specify the name of the directory as well or change the directory name to be something like gz_chunks. This is only after all data belonging to a single policy run are stored in a single directory.