added code of conduct

Author: lh3

code_of_conduct.md

@@ -0,0 +1,30 @@
+## Contributor Code of Conduct
+
+As contributors and maintainers of this project, we pledge to respect all
+people who contribute through reporting issues, posting feature requests,
+updating documentation, submitting pull requests or patches, and other
+activities.
+
+We are committed to making participation in this project a harassment-free
+experience for everyone, regardless of level of experience, gender, gender
+identity and expression, sexual orientation, disability, personal appearance,
+body size, race, age, or religion.
+
+Examples of unacceptable behavior by participants include the use of sexual
+language or imagery, derogatory comments or personal attacks, trolling, public
+or private harassment, insults, or other unprofessional conduct.
+
+Project maintainers have the right and responsibility to remove, edit, or
+reject comments, commits, code, wiki edits, issues, and other contributions
+that are not aligned to this Code of Conduct. Project maintainers or
+contributors who do not follow the Code of Conduct may be removed from the
+project team.
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported by opening an issue or contacting the maintainer via email.
+
+This Code of Conduct is adapted from the [Contributor Covenant][cc], [version
+1.0.0][v1].
+
+[cc]: http://contributor-covenant.org/
+[v1]: http://contributor-covenant.org/version/1/0/0/