* Add Code of Conduct and Contribution Guidelines

Add a full Code of Conduct and Code Contribution Guidelines document.
Provide description on how best to retrieve code, fork, checkout, and commit changes.

Fixes #688

* Update steps for git push

* Update based on PR comments

Removed several linkable sections in the Code of Conduct.
Update contributing to use kafka-go consistently.
Finished explaining how to replace the original version with forked version of the library.

* Update based on further feedback

* Adjust to follow the twilio-go code of contact