Node.js Governance Policy

With #11, we have had a rich discussion around Code of Conduct. We need to move forward on governance, so I have removed the proposals for Code of Conduct and Contribution Policy with the hope of more effectively iterating on each of these giving the the attention and discussion that they merit.

@mikeal [mentions in the original post](https://github.com/joyent/nodejs-advisory-board/pull/11#issue-48739582) the context for these files:

>They are adapted from Node Forward's fork where they are sections in the CONTRIBUTING file. Here I've put them in to their own files for clearer separation. All direct references to Node Forward have been removed so that this can be adopted by any project without confusion.
>
>The premise is simple: the project employs a simple governance structure that can be the "final word" on contentious issues and, most importantly, owns the contribution policy. The contribution policy is intended to be somewhat fluid and adapt over time to the needs of the project. The current one is geared heavily towards growing the contributor base of the project because that's the biggest problem. You can imagine that after the project grows a large cohort of contributors this policy would change to adapt the challenges of distributing work among a larger contributor base.