Add CONTRIBUTING.md

CONTRIBUTING.md

@@ -0,0 +1,9 @@
+# Contribution Guidelines
+
+I welcome contributions to ExTwilio. Contributors should keep in mind the following rules:
+
+- Pull requests will not be accepted if the Travis build is failing.
+- Code changes should be accompanied with test changes or additions to validate that your changes actually work.
+- Code changes must update inline documentaiton in all relevant areas. Users rely on this documentation.
+- Any code you submit will be subject to the MIT license.
+- Discussion must be courteous at all times. Offending discussions will be closed and locked.

README.md

@@ -129,9 +129,13 @@ ExTwilio.Call.destroy(call)
 
 For more in-depth documentation, see the generated docs for each module.
 
+## Contributing
+
+See the [CONTRIBUTING.md](CONTRIBUTING.md) file for contribution guidelines.
+
 ## License
 ExTwilio is licensed under the MIT license. For more details, see the `LICENSE` file at the root of the repository. It depends on Elixir, which is under the Apache 2 license.
 
 Twilio<sup>TM</sup> is trademark of Twilio, Inc.
 
-[hex]: http://hex.pm
+[hex]: http://hex.pm