Reformat CONTRIBUTING.md

- some reformatting to make it better readable in smaller terminals
- adds a note that suggests validating DCO before pushing

Signed-off-by: funkyfuture <[email protected]>

CONTRIBUTING.md

@@ -1,6 +1,8 @@
 # Contributing to Compose
 
-Compose is a part of the Docker project, and follows the same rules and principles. Take a read of [Docker's contributing guidelines](https://github.com/docker/docker/blob/master/CONTRIBUTING.md) to get an overview.
+Compose is a part of the Docker project, and follows the same rules and
+principles. Take a read of [Docker's contributing guidelines](https://github.com/docker/docker/blob/master/CONTRIBUTING.md)
+to get an overview.
 
 ## TL;DR
 
@@ -17,28 +19,40 @@ If you're looking contribute to Compose
 but you're new to the project or maybe even to Python, here are the steps
 that should get you started.
 
-1. Fork [https://github.com/docker/compose](https://github.com/docker/compose) to your username.
-1. Clone your forked repository locally `git clone [email protected]:yourusername/compose.git`.
-1. Enter the local directory `cd compose`.
-1. Set up a development environment by running `python setup.py develop`. This will install the dependencies and set up a symlink from your `docker-compose` executable to the checkout of the repository. When you now run `docker-compose` from anywhere on your machine, it will run your development version of Compose.
+1. Fork [https://github.com/docker/compose](https://github.com/docker/compose)
+   to your username.
+2. Clone your forked repository locally `git clone [email protected]:yourusername/compose.git`.
+3. Enter the local directory `cd compose`.
+4. Set up a development environment by running `python setup.py develop`. This
+   will install the dependencies and set up a symlink from your `docker-compose`
+   executable to the checkout of the repository. When you now run
+   `docker-compose` from anywhere on your machine, it will run your development
+   version of Compose.
 
 ## Running the test suite
 
-Use the test script to run linting checks and then the full test suite:
+Use the test script to run DCO check, linting checks and then the full test
+suite against different Python interpreters:
 
     $ script/test
 
-Tests are run against a Docker daemon inside a container, so that we can test against multiple Docker versions. By default they'll run against only the latest Docker version - set the `DOCKER_VERSIONS` environment variable to "all" to run against all supported versions:
+Tests are run against a Docker daemon inside a container, so that we can test
+against multiple Docker versions. By default they'll run against only the latest
+Docker version - set the `DOCKER_VERSIONS` environment variable to "all" to run
+against all supported versions:
 
     $ DOCKER_VERSIONS=all script/test
 
-Arguments to `script/test` are passed through to the `nosetests` executable, so you can specify a test directory, file, module, class or method:
+Arguments to `script/test` are passed through to the `nosetests` executable, so
+you can specify a test directory, file, module, class or method:
 
     $ script/test tests/unit
     $ script/test tests/unit/cli_test.py
     $ script/test tests.integration.service_test
     $ script/test tests.integration.service_test:ServiceTest.test_containers
 
+Before pushing a commit you can check the DCO by invoking `script/validate-dco`.
+
 ## Building binaries
 
 Linux:
@@ -49,27 +63,23 @@ OS X:
 
     $ script/build-osx
 
-Note that this only works on Mountain Lion, not Mavericks, due to a [bug in PyInstaller](http://www.pyinstaller.org/ticket/807).
+Note that this only works on Mountain Lion, not Mavericks, due to a
+[bug in PyInstaller](http://www.pyinstaller.org/ticket/807).
 
 ## Release process
 
 1. Open pull request that:
-
  - Updates the version in `compose/__init__.py`
  - Updates the binary URL in `docs/install.md`
  - Updates the script URL in `docs/completion.md`
  - Adds release notes to `CHANGES.md`
-
 2. Create unpublished GitHub release with release notes
-
-3. Build Linux version on any Docker host with `script/build-linux` and attach to release
-
-4. Build OS X version on Mountain Lion with `script/build-osx` and attach to release as `docker-compose-Darwin-x86_64` and `docker-compose-Linux-x86_64`.
-
+3. Build Linux version on any Docker host with `script/build-linux` and attach
+   to release
+4. Build OS X version on Mountain Lion with `script/build-osx` and attach to
+   release as `docker-compose-Darwin-x86_64` and `docker-compose-Linux-x86_64`.
 5. Publish GitHub release, creating tag
-
 6. Update website with `script/deploy-docs`
-
 7. Upload PyPi package
 
         $ git checkout $VERSION