Github now supports issue templates via a markdown file called issue_template.md in the root or .github/ folder of your repo!
There is also added support for pull request templates via a markdown file called pull_request_template.md in the root or .github/ folder of your repo!
https://github.com/samccone/issue-template/issues/new
For a more in-depth explanation check out: https://help.github.com/articles/helping-people-contribute-to-your-project/
To generate template customized to your project, check out: Issue and Pull Request Templates Generator