Provide helper namespaces for contributed workflows

[oubiwann]

After fully integrating the examples into this repo (see #43), and recommending a backwards-compatible approach for simplifying workflow configuration (see #49), it might make sense to provide wrappers (in their own namespaces) for workflows against commonly used/contributed services.

Open questions:

• How supported will these be?
  • provide caveat in the ns docstring
• Is there a good way to provide testing for them? (Does the service in question provide testing credentials for public use?)
• Can a testing approach be integrated with TravisCI?

Part of release #64