Adds copy of metaflow's helloworld example

[elijahbenizzy]

[Short description explaining the high-level reason for the pull request]

Additions

Removals

Changes

Testing

Screenshots

If applicable

Notes

Todos

Checklist

• [ ] PR has an informative and human-readable title
• [ ] Changes are limited to a single goal (no scope creep)
• [ ] Code can be automatically merged (no conflicts)
• [ ] Code follows the standards laid out in the TODO link to standards
• [ ] Passes all existing automated tests
• [ ] Any change in functionality is tested
• [ ] New functions are documented (with a description, list of inputs, and expected output)
• [ ] Placeholder code is flagged / future todos are captured in comments
• [ ] Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• [ ] Reviewers requested with the Reviewers tool :arrow_right:

Testing checklist

Python

• [ ] python 3.6
• [ ] python 3.7