REL: 0.6.1

[effigies]

Summary

Proposing releasing version 0.6.1 in order to get pydra.tasks namespace package into a PyPI-released version.

Adds changelog to docs.

Checklist

• All tests passing
• I have added tests to cover my changes
• I have updated documentation (if necessary)
• My code follows the code style of this project
  (we are using black: you can pip install pre-commit,
  run pre-commit install in the pydra directory
  and black will be run automatically with each commit)

Acknowledgment

• I acknowledge that this contribution will be available under the Apache 2 license.

[effigies]

Example docs: https://431-152126811-gh.circle-artifacts.com/0/docs/_build/no_version_html/html/changes.html

[djarecka]

@effigies - thanks!

[effigies]

Don't see an advantage to waiting on Travis tests for a doc build. Will merge and release. Thanks for having a look.