*: add contribution guide and DCO

Not sure why these have been missing for so long.
Pulled from coreos/template-project as per other
CoreOS projects.

Author: jonboulle

CONTRIBUTING.md

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+# How to Contribute
+
+CoreOS projects are [Apache 2.0 licensed](LICENSE) and accept contributions via
+GitHub pull requests.  This document outlines some of the conventions on
+development workflow, commit message formatting, contact points and other
+resources to make it easier to get your contribution accepted.
+
+# Certificate of Origin
+
+By contributing to this project you agree to the Developer Certificate of
+Origin (DCO). This document was created by the Linux Kernel community and is a
+simple statement that you, as a contributor, have the legal right to make the
+contribution. See the [DCO](DCO) file for details.
+
+# Email and Chat
+
+The project currently uses the general CoreOS email list and IRC channel:
+- Email: [coreos-dev](https://groups.google.com/forum/#!forum/coreos-dev)
+- IRC: #[coreos](irc://irc.freenode.org:6667/#coreos) IRC channel on freenode.org
+
+Please avoid emailing maintainers found in the MAINTAINERS file directly. They
+are very busy and read the mailing lists.
+
+## Getting Started
+
+- Fork the repository on GitHub
+- Read the [README](README.md) for build and test instructions
+- Play with the project, submit bugs, submit patches!
+
+## Contribution Flow
+
+This is a rough outline of what a contributor's workflow looks like:
+
+- Create a topic branch from where you want to base your work (usually master).
+- Make commits of logical units.
+- Make sure your commit messages are in the proper format (see below).
+- Push your changes to a topic branch in your fork of the repository.
+- Make sure the tests pass, and add any new tests as appropriate.
+- Submit a pull request to the original repository.
+
+Thanks for your contributions!
+
+### Coding Style
+
+CoreOS projects written in Go follow a set of style guidelines that we've documented 
+[here](https://github.com/coreos/docs/tree/master/golang). Please follow them when 
+working on your contributions.
+
+### Format of the Commit Message
+
+We follow a rough convention for commit messages that is designed to answer two
+questions: what changed and why. The subject line should feature the what and
+the body of the commit should describe the why.
+
+```
+scripts: add the test-cluster command
+
+this uses tmux to setup a test cluster that you can easily kill and
+start for debugging.
+
+Fixes #38
+```
+
+The format can be described more formally as follows:
+
+```
+<subsystem>: <what changed>
+<BLANK LINE>
+<why this change was made>
+<BLANK LINE>
+<footer>
+```
+
+The first line is the subject and should be no longer than 70 characters, the
+second line is always blank, and other lines should be wrapped at 80 characters.
+This allows the message to be easier to read on GitHub as well as in various
+git tools.

DCO

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+Developer Certificate of Origin
+Version 1.1
+
+Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+660 York Street, Suite 102,
+San Francisco, CA 94110 USA
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+
+
+Developer's Certificate of Origin 1.1
+
+By making a contribution to this project, I certify that:
+
+(a) The contribution was created in whole or in part by me and I
+    have the right to submit it under the open source license
+    indicated in the file; or
+
+(b) The contribution is based upon previous work that, to the best
+    of my knowledge, is covered under an appropriate open source
+    license and I have the right under that license to submit that
+    work with modifications, whether created in whole or in part
+    by me, under the same open source license (unless I am
+    permitted to submit under a different license), as indicated
+    in the file; or
+
+(c) The contribution was provided directly to me by some other
+    person who certified (a), (b) or (c) and I have not modified
+    it.
+
+(d) I understand and agree that this project and the contribution
+    are public and that a record of the contribution (including all
+    personal information I submit with it, including my sign-off) is
+    maintained indefinitely and may be redistributed consistent with
+    this project or the open source license(s) involved.