Add support for sse-s3 encryption with vault as KMS.
Also refactoring code to make use of headers and functions defined in
crypto package and clean up duplicated code.
With following changes
- Add SSE and refactor encryption API (#942) <Andreas Auernhammer>
- add copyObject test changing metadata and preserving etag (#944) <Harshavardhana>
- Add SSE-C tests for multipart, copy, get range operations (#941) <Harshavardhana>
- Removing conditional check for notificationInfoCh in api-notication (#940) <Matthew Magaldi>
- Honor prefix parameter in ListBucketPolicies API (#929) <kannappanr>
- test for empty objects uploaded with SSE-C headers (#927) <kannappanr>
- Encryption headers should also be set during initMultipart (#930) <Harshavardhana>
- Add support for Content-Language metadata header (#928) <kannappanr>
- Fix check for duplicate notification configuration entries (#917) <kannappanr>
- allow OS to cleanup sockets in TIME_WAIT (#925) <Harshavardhana>
- Sign V2: Fix signature calculation in virtual host style (#921) <A. Elleuch>
- bucket policy: Support json string in Principal field (#919) <A. Elleuch>
- Fix copyobject failure for empty files (#918) <kannappanr>
- Add new constructor NewWithOptions to SDK (#915) <poornas>
- Support redirect headers to sign again with new Host header. (#829) <Harshavardhana>
- Fail in PutObject if invalid user metadata is passed <Harshavadhana>
- PutObjectOptions Header: Don't include invalid header <Isaac Hess>
- increase max retry count to 10 (#913) <poornas>
- Add new regions for Paris and China west. (#905) <Harshavardhana>
- fix s3signer to use req.Host header (#899) <Bartłomiej Nogaś>
