compare s3's last modified time using server's timezone

S3's last modified time is stored in utc timezone,
but displayed in server's timezone.
Prior to this fix, no timezone calculation was made,
so test_ls_command.py kept failing for some timezones.

This fix tests displayed last modified time using server's timezone.
Remove dateutil as a dep, not needed

botocore pulls in a dep on dateutil.
Merge branch 'quiver-fix-s3-lastmodified-tz-oddity' into develop

* quiver-fix-s3-lastmodified-tz-oddity:
  Remove dateutil as a dep, not needed
  compare s3's last modified time using server's timezone