add proposed code of conduct from http://contributor-covenant.org

CODE_OF_CONDUCT.md

@@ -0,0 +1,22 @@
+# Contributor Code of Conduct
+
+As contributors and maintainers of this project, and in the interest of fostering an open and welcoming community, 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, ethnicity, age, religion, or nationality.
+
+Examples of unacceptable behavior by participants include:
+
+* The use of sexualized language or imagery
+* Personal attacks
+* Trolling or insulting/derogatory comments
+* Public or private harassment
+* Publishing other's private information, such as physical or electronic addresses, without explicit permission
+* Other unethical or 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. By adopting this Code of Conduct, project maintainers commit themselves to fairly and consistently applying these principles to every aspect of managing this project. Project maintainers who do not follow or enforce the Code of Conduct may be permanently removed from the project team.
+
+This code of conduct applies both within project spaces and in public spaces when an individual is representing the project or its community.
+
+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 1.2.0, available at [http://contributor-covenant.org/version/1/2/0/](http://contributor-covenant.org/version/1/2/0/)

README.md

@@ -22,6 +22,10 @@ For further information see [http://mapnik.org](http://mapnik.org) and also our
 
 See [INSTALL.md](https://github.com/mapnik/mapnik/blob/master/INSTALL.md) for installation instructions and the [Install](https://github.com/mapnik/mapnik/wiki/Mapnik-Installation) page on the wiki for guides.
 
+# Code of Conduct
+
+Please note that this project is released with a [Contributor Code of Conduct](https://github.com/mapnik/mapnik/blob/master/CODE_OF_CONDUCT.md). By participating in this project you agree to abide by its terms.
+
 # License
 
 Mapnik software is free and is released under the LGPL ([GNU Lesser General Public License](http://www.gnu.org/licenses/lgpl.html_)). Please see [COPYING](https://github.com/mapnik/mapnik/blob/master/COPYING) for more information.