minor clarifications in gsutil stat help
minor clarifications in gsutil stat help

dimfeld/gsutil,BrandonY/gsutil,dtjackson/gsutil,GoogleCloudPlatform/gsutil,GoogleCloudPlatform/gsutil,ttiurani/gsutil,chriskuehl/gsutil-debian,mattdr/gsutil,craigcitro/gsutil,fishjord/gsutil