Merge branch 'hotfix/3604'

Close #3604
Merge branch 'develop'

Preparing to tag 2.1.0 -- all new features from develop are now merged to master.
[2.1.0] Release updates

- Updated CHANGELOG
- Updated README
- Updated Zend\Version
Merge branch 'releases/2.1.0' into develop

Prepping 2.1.0 release