Working toward making it easier to add new SegmentPullers.

1) Move the local cacheFile logic out of the S3 pullers into the SingleSegmentLoader
2) Make the S3SegmentPuller just pull down the file
3) Make the Loader do the unzip, ungzip, or rename
4) 2 and 3 make S3ZippedSegmentPuller not necessary (still there, just deprecated and empty)
4) Tweak the TaskToolbox so that the Pullers returned by getSegmentGetters behave the same as they did before