PULL_REQUEST_TEMPLATE.md

What changes were proposed in this pull request?

(Please fill in changes proposed in this fix)

Is this related to an already existing issue on sparkler?
If so, mention that issue by referencing its number here.

Will it close an existing issue?
Say 'Closes #IssueNum' here.

How was this patch tested?

We are particularly interested in unit tests, integration tests, manual tests you did to ensure that the patch works as expected, so briefly describe them.

Please review https://github.com/USCDataScience/sparkler/blob/master/.github/CONTRIBUTING.md before opening a pull request.