Amend version of contributing.md from feedback

- Add OS info request in reporting issues section
- Add PR subsection about clear, logical commits
- Add section describing how to set up a dev environment

Signed-off-by: Joffrey F <joffrey@docker.com>

CONTRIBUTING.md

@@ -15,6 +15,7 @@ the following information:
 ```
 pip freeze | grep docker-py && python --version && docker version
 ```
+- OS, distribution and OS version
 - The issue you're encountering including a stacktrace if applicable
 - If possible, steps or a code snippet to reproduce the issue
 
@@ -41,34 +42,61 @@ broken by your changes by running the test suite. You can do so simply by
 running `make test` in the project root. This also includes coding style using
 `flake8`
 
-### 3. Rebase proactively
+### 3. Write clear, self-contained commits
+
+Your commit message should be concise and describe the nature of the change.
+The commit itself should make sense in isolation from the others in your PR.
+Specifically, one should be able to review your commit separately from the
+context.
+
+### 4. Rebase proactively
 
 It's much easier to review a pull request that is up to date against the
 current master branch.
 
-### 4. Notify thread subscribers when changes are made
+### 5. Notify thread subscribers when changes are made
 
 GitHub doesn't notify subscribers when new commits happen on a PR, and
 fixes or additions might be missed. Please add a comment to the PR thread
 when you push new changes.
 
-### 5. Two maintainers LGTM are required for merging
+### 6. Two maintainers LGTM are required for merging
 
 Please wait for review and approval of two maintainers, and respond to their
 comments and suggestions during review.
 
-### 6. Add tests
+### 7. Add tests
 
 Whether you're adding new functionality to the project or fixing a bug, please
 add relevant tests to ensure the code you added continues to work as the
 project evolves.
 
-### 7. Add docs
+### 8. Add docs
 
 This usually applies to new features rather than bug fixes, but new behavior
 should always be documented.
 
-### 8. Ask questions
+### 9. Ask questions
 
 If you're ever confused about something pertaining to the project, feel free
 to reach out and ask questions. We will do our best to answer and help out.
+
+
+## Development environment
+
+If you're looking contribute to docker-py but are new to the project or Python,
+here are the steps to get you started.
+
+1. Fork [https://github.com/docker/docker-py](https://github.com/docker/docker-py)
+   to your username.
+2. Clone your forked repository locally with
+  `git clone git@github.com:yourusername/docker-py.git`.
+3. Configure a
+  [remote](https://help.github.com/articles/configuring-a-remote-for-a-fork/)
+  for your fork so that you can
+  [sync changes you make](https://help.github.com/articles/syncing-a-fork/)
+  with the original repository.
+4. Enter the local directory `cd docker-py`.
+5. Run `python setup.py develop` to install the dev version of the project
+  and required dependencies. We recommend you do so inside a
+  [virtual environment](http://docs.python-guide.org/en/latest/dev/virtualenvs)