Update version for patch release to 0.3.1

[sandrahoang686]

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• Why *** did I do it? (What was the motivation?)

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Fixes or Addresses Issue #: [ticket number & link]

Checklist before requesting a review:

• [ ] My code follows the guidelines of this project
• [ ] I performed a self-review of my code changes
• [ ] I have added my changes to the change log (HISTORY.rst)
• [ ] I have completed spell-checking, removed unnecessary print statements & commented-out code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] New and existing unit tests pass locally with my changes