Added contribution guidelines

Signed-off-by: Elton Stoneman <elton@sixeyed.com>

Author: sixeyed

CONTRIBUTING.md

@@ -0,0 +1,15 @@
+## Contributing to Image2Docker ##
+
+Thank you so much for your interest in contributing to the Image2Docker tool ("i2d2"). Docker has open source in its DNA, and has always worked closely with the community.
+
+Just a few quick things to be aware of before you get started.
+
+We welcome issues and [signed pull requests](https://github.com/docker/docker/blob/master/CONTRIBUTING.md#sign-your-work) for either adding new features, or fixing a problem with an existing feature. 
+
+Anything you contribute will be under an Apache license. Docker will choose which PRs to accept and reject. Anything posted here may be forked by anyone on GitHub.
+
+We will be following the lightweight version of the Docker contribution policies and procedures as explained in
+- [Docker documentation](https://docs.docker.com)
+- The [Docker engine repo](https://github.com/docker/docker/blob/master/CONTRIBUTING.md).
+
+This largely boils down to [signing your PRs](https://github.com/docker/docker/blob/master/CONTRIBUTING.md#sign-your-work), following the Docker [trademark guidelines](https://www.docker.com/trademark-guidelines), and following the community guidelines.