update issue template (issue #502)

[Pandademic]

Make sure these boxes are checked before your pull request (PR) is ready to be reviewed and merged. Thanks!

• [ ] tests pass -- look for a green checkbox ✔️ a few minutes after opening your PR -- or run tests locally with rake test
• [x] code is in uniquely-named feature branch and has no merge conflicts
• [ x] PR is descriptively titled
• [x] PR body includes fixes #0000-style reference to original issue #
• [x] ask @publiclab/reviewers for help, in a comment below Tested failed on nodejs 8 , but this is almost docs. This fixes #502.

[welcome[bot]]

Thanks for opening this pull request! Dangerbot will test out your code and reply in a bit with some pointers and requests. There may be some errors, but don't worry! We're here to help! 👍🎉😄

[Pandademic]

@publiclab/reviewers , is this good?