Return the part/key so that the user can manage multipart uploads

Currently uploading a part does not return the key. The key is
important as it contains the server generated etag which may
then be used by the user to complete the multipart upload
without asking the server for a list of parts.
Add unit test for getting the etag from the uploaded part.
Merge branch 'release-2.11.0' into develop

* release-2.11.0:
  Bumping version to 2.11.0
Added the v2.11.0 release notes to the index.
Added a in-development release notes doc for the next release.
Updated Elasticache to support Redis & replication.
Updated the user-agent string Boto uses.
Fixed #1687 - Headers involved with signing sent with S3 keys should be case-insensitive for the user.
Fix glacier layer2.list_vaults and related tests.
support other ELB policies

Also add missing files from ec2/elb to the doc index.
Merge pull request #1675 from tpodowd/mpu_return_part_for_etag

Return the part/key so that the user can manage multipart uploads. Fixes #1675, #1305.
Merge branch 's3-signed-headers-case' into develop
Merge remote-tracking branch 'egirshov/elb' into develop
Merge remote-tracking branch 'kmwang/fix-glacier-list-vaults' into develop
Added docs about the included CLI tools & recommended people check out the AWS-CLI.
Merge branch 'elasticache-redis' into develop
Added notes for the release.
Bumping version to 2.12.0
Merge branch 'release-2.12.0'

* release-2.12.0:
  Bumping version to 2.12.0
  Added notes for the release.
  Added docs about the included CLI tools & recommended people check out the AWS-CLI.
  support other ELB policies
  Fix glacier layer2.list_vaults and related tests.
  Fixed #1687 - Headers involved with signing sent with S3 keys should be case-insensitive for the user.
  Updated the user-agent string Boto uses.
  Updated Elasticache to support Redis & replication.
  Added a in-development release notes doc for the next release.
  Added the v2.11.0 release notes to the index.
  Add unit test for getting the etag from the uploaded part.
  Return the part/key so that the user can manage multipart uploads