[EMR] Add a working streaming steps example to add-steps and create-cluster
Add ``opsworks register`` command.

It registers an EC2 instance or machine with AWS OpsWorks
Update requirements and changelog for opsworks
Update changelog with service updates
Bumping version to 1.6.7
Merge branch 'release-1.6.7' into develop

* release-1.6.7:
  Bumping version to 1.6.7
  Update changelog with service updates
  Update requirements and changelog for opsworks
  Add ``opsworks register`` command.
  [EMR] Add a working streaming steps example to add-steps and create-cluster