update README and CONTRIBUTING with link to CoC file

[skip ci]

CONTRIBUTING.md

@@ -1,42 +1,33 @@
 # Issue and Pull Request Guidelines
 
-Thank you for getting involved in making Nokogiri better!
+Thank you for helping make Nokogiri better!
 
 
 ## Code of Conduct
 
-For best results, be nice. Remember that Nokogiri maintainers are
-volunteers, and treat them with respect.
+Our full Code of Conduct is in [`CODE_OF_CONDUCT.md`](CODE_OF_CONDUCT.md).
 
-Do not act entitled to service. Do not be rude. Do not use judgmental
-or foul language.
+For best results, be nice. Remember that Nokogiri maintainers are volunteers, and treat them with respect.
 
-The maintainers reserve the right to delete comments that are rude, or
-that contain foul language. The maintainers reserve the right to
-delete comments that they deem harassing or offensive.
+Do not act entitled to service. Do not be rude. Do not use judgmental or foul language.
+
+The maintainers reserve the right to delete comments that are rude, or that contain foul language. The maintainers reserve the right to delete comments that they deem harassing or offensive.
 
 
 ## Issues
 
-Please read the
-["Getting Help" tutorial](http://www.nokogiri.org/tutorials/getting_help.html)
-at the [nokogiri.org](http://nokogiri.org) site.
+Please read the ["Getting Help" tutorial](http://www.nokogiri.org/tutorials/getting_help.html) at the [nokogiri.org](http://nokogiri.org) site.
 
 If you're reporting an issue, it must contain:
 
 * Example code that reproduces the **observed** behavior.
 * An explanation of what the **expected** behavior is.
 
-That's it. If you don't provide that information, we'll ask you for
-it, tag the story "needs more information", and then after a time will
-close it if the information isn't provided.
+That's it. If you don't provide that information, we'll ask you for it, tag the story "needs more information", and then after a time will close it if the information isn't provided.
 
 
 ## Pull Requests
 
-Pull requests must always contain a test to prevent
-regressions. Preferably, the test should demonstrate the __intent__ of
-the code.
+Pull requests must always contain a test to prevent regressions. Preferably, the test should demonstrate the __intent__ of the code.
 
-We may ask you for clarification if we don't understand the intent of
-the change.
+We may ask you for clarification if we don't understand the intent of the change.

README.md

@@ -179,6 +179,12 @@ explicitly setting the encoding to EUC-JP on the parser:
   bundle exec rake
 ```
 
+
+## Code of Conduct
+
+We've adopted the Contributor Covenant code of conduct, which you can read in full in [`CODE_OF_CONDUCT.md`](CODE_OF_CONDUCT.md).
+
+
 ## License
 
 This project is licensed under the terms of the MIT license.