Add Contributor Code of Conduct

Author: willdurand

README.md

@@ -530,6 +530,36 @@ Credits
 * [All contributors](https://github.com/geocoder-php/Geocoder/contributors)
 
 
+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 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 one or more of the project
+maintainers.
+
+This Code of Conduct is adapted from the [Contributor
+Covenant](http:contributor-covenant.org), version 1.0.0, available at
+[http://contributor-covenant.org/version/1/0/0/](http://contributor-covenant.org/version/1/0/0/)
+
+
 License
 -------