Add `force` kwarg for s3s3.api.upload.
Add `force` kwarg for s3s3.api.upload.

    * Change order operations so we fail early and do any real
      IO as late as possible.
    * Thanks @chrisbrue for `force` idea.

	modified:   s3s3/api.py

lsst-sqre/s3-glacier,lsst-sqre/s3s3