v2.1.0.RELEASE

Change log:

9bb86b7 Upgrade to SC-AWS-2.1.1l prepare release
f4d22d5 Prepare for 2.1.0.RELEASE
82c0135 GH-116: Document optional dependencies
e5acf0f Upgrade dependencies; fix for compatibility
0995564 GH-106: Allow null for S3MH.objectAclExpression
432d8b6 Start 2.1.0 version
a3dd476 Add note about project version and its deps