Boto overwrites the Header Content-Type setting with its own guess. Changed _save to add the Content-Type to the metadata. The metadata is added to the Header after boto overwrites the Content-Type in the Header.
In the case of uploaded files, the file's content_type is ignored and instead mimetypes.guess_type is used instead. This fix checks for content.content_type and if present, uses it instead of mimetypes.guess_type.
We needed this fix to properly set the Content-Type when uploading caf files without an extension.