PULL_REQUEST_TEMPLATE.md

What does this implement/fix? Explain your changes.

...

Does this close any currently open issues?

...

Any other comments?

...

Checklist

Check all those that are applicable and complete.

• Merged with latest master branch
• Regenerate documentation with npm run docs
• Add change details to CHANGELOG.md under "Next" section
• Added examples for testing to examples/ directory
• Travis CI passes (Mac support)
• AppVeyor passes (Windows support)