Add a PR template (#37)

Suggestions welcome. Should go in all the repos once it's approved.

.github/pull_request_template.md

@@ -0,0 +1,29 @@
+# Description
+
+*Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.*
+
+## Related issue(s)
+
+- Issue: #<issue_number_here>
+- See also:
+    - #<issue_number>
+
+## Type of change
+
+- [ ] Bug fix (non-breaking change which fixes an issue)
+- [ ] New feature (non-breaking change which adds functionality)
+- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
+- [ ] Documentation
+- [ ] Other (please describe):
+
+# How has this been tested?
+
+*Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce.*
+
+# Checklist
+
+- [ ] I have performed a self-review of my own code.
+- [ ] I have commented my code, particularly in hard-to-understand areas.
+- [ ] I have updated the documentation, if necessary.
+- [ ] I added tests for my changes, and/or the testing strategy is described above.
+- [ ] I updated the [changelog](../CHANGELOG.md).