PULL_REQUEST_TEMPLATE

Checklist for prospect students for Google Summer of Code 2017:

- [ ] I contacted NumFOCUS mentors before writing my proposal
- [ ] I showed you my contribution (it can be any form: proof-of-concept project idea, some sample code or just a link to your commits from other project)
- [ ] I linked to my sample contribution from the proposal
- [ ] I linked to my opened issues in numfocus/gsoc repository from the proposal