Add assertions for content type in integration specs
Set content-type on uploaded gz files so they don't get the S3 default of 'application/x-gzip' which browsers don't seem to like.
Fix extraction of uncompressed filename for .gz mime type setting
Fix specs, a gzipped file should retain original content type yet have a content encoding of gzip
Version 0.5.3, improved handling content type / content encoding for gzipped files