Added Code of Conduct (http://contributor-covenant.org/version/1/4/code_of_conduct.md) and a Contributing section in the README.

Author: boredzo

CODE OF CONDUCT.md

@@ -0,0 +1,74 @@
+# Contributor Covenant Code of Conduct
+
+## Our Pledge
+
+In the interest of fostering an open and welcoming environment, we as
+contributors and maintainers pledge to making participation in our project and
+our community a harassment-free experience for everyone, regardless of age, body
+size, disability, ethnicity, gender identity and expression, level of experience,
+nationality, personal appearance, race, religion, or sexual identity and
+orientation.
+
+## Our Standards
+
+Examples of behavior that contributes to creating a positive environment
+include:
+
+* Using welcoming and inclusive language
+* Being respectful of differing viewpoints and experiences
+* Gracefully accepting constructive criticism
+* Focusing on what is best for the community
+* Showing empathy towards other community members
+
+Examples of unacceptable behavior by participants include:
+
+* The use of sexualized language or imagery and unwelcome sexual attention or
+advances
+* Trolling, insulting/derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or electronic
+  address, without explicit permission
+* Other conduct which could reasonably be considered inappropriate in a
+  professional setting
+
+## Our Responsibilities
+
+Project maintainers are responsible for clarifying the standards of acceptable
+behavior and are expected to take appropriate and fair corrective action in
+response to any instances of unacceptable behavior.
+
+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, or to ban temporarily or
+permanently any contributor for other behaviors that they deem inappropriate,
+threatening, offensive, or harmful.
+
+## Scope
+
+This Code of Conduct applies both within project spaces and in public spaces
+when an individual is representing the project or its community. Examples of
+representing a project or community include using an official project e-mail
+address, posting via an official social media account, or acting as an appointed
+representative at an online or offline event. Representation of a project may be
+further defined and clarified by project maintainers.
+
+## Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported by contacting the project team at git (U+0040 COMMERCIAL AT) boredzo.org. All
+complaints will be reviewed and investigated and will result in a response that
+is deemed necessary and appropriate to the circumstances. The project team is
+obligated to maintain confidentiality with regard to the reporter of an incident.
+Further details of specific enforcement policies may be posted separately.
+
+Project maintainers who do not follow or enforce the Code of Conduct in good
+faith may face temporary or permanent repercussions as determined by other
+members of the project's leadership.
+
+## Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 1.4,
+available at [http://contributor-covenant.org/version/1/4][version]
+
+[homepage]: http://contributor-covenant.org
+[version]: http://contributor-covenant.org/version/1/4/

README.md

@@ -173,6 +173,34 @@ I use [Rick McCarty's algorithm for converting calendar dates to week dates](htt
 
 * There is no method to analyze a date string and tell you what was found in it (year, month, week, day, ordinal day, etc.). Feel free to submit a patch.
 
+## Contributing
+
+This project adheres to [the Contributor Covenant, version 1.4](CODE OF CONDUCT.md). Please read that before deciding whether you are willing to contribute.
+
+You're welcome to work on any open bug in the issue tracker, but we do have some that are [up-for-grabs](https://github.com/boredzo/iso-8601-date-formatter/issues?q=is%3Aissue+is%3Aopen+label%3Aup-for-grabs) that are particularly easy or potentially interesting.
+
+Please don't break compatibility with old OS versions (OS X 10.7/iOS 4) until work begins on the 1.0 release. That won't happen until 0.9 is done, and starting 1.0-only work (e.g., ARCification) early will lead to conflicts.
+
+The tests use ARC, but the formatter itself does not ([yet](https://github.com/boredzo/iso-8601-date-formatter/issues/21)). Please be sure to add the needed `release` or `autorelease` messages when adding code that creates objects.
+
+Adding test cases is highly encouraged, especially if adding new functionality. Ideally, please test a comprehensive set of:
+
+- success cases
+- failure cases
+- exception (programmer error) cases: even if something isn't supported, the behavior should still be reliable and preferably diagnostically helpful
+
+Travis CI will run the tests automatically when you submit a pull request, and a PR with failing tests will not be accepted.
+
+Contributions consisting of nothing but test cases are welcome. If one/some of those cases fail, please include fixes, or at least, submit an issue report for the failure(s) and surround the failing tests with:
+
+    #if FIXED_(issue number)
+    - (void) test_thingThatDoesntWorkButShould {
+        ⋮
+    }
+    #endif FIXED_(issue number)
+
+As far as code style, mostly, please try to remain consistent with the existing code. Please do add nullability annotations (`ISO8601_NULLABLE`/`ISO8601_NONNULL`) and `const` to new code whenever applicable.
+
 ## Copyright
 
 This code is copyright 2006–2016 Peter Hosey. It is under the BSD license; see LICENSE.txt for the full text of the license.