Add encrypted uploads

[etspaceman]

This library should be able to support both the server-side and client-side encryption upload options that S3 provides.

[EECOLOR]

You're welcome to create a pull request that adds the feature.

If you feel this is not something you are able to do please provide some links to the corresponding documentation. It would be awesome if you would provide a test case that shows the expected behavior and would turn green once the feature is implemented.