Split out release process

To aid clarity in how to contribute, I've moved the release process
out into it's own RELEASE_PROCESS.md file. The release process info
is only relevant for maintainers who are building new releases of
compose.

Signed-off-by: Mazz Mosley <mazz@houseofmnowster.com>

RELEASE_PROCESS.md

@@ -0,0 +1,36 @@
+# Building a Compose release
+
+## Building binaries
+
+`script/build-linux` will build the Linux binary inside a Docker container:
+
+    $ script/build-linux
+
+`script/build-osx` will build the Mac OS X binary inside a virtualenv:
+
+    $ script/build-osx
+
+For official releases, you should build inside a Mountain Lion VM for proper
+compatibility. Run the this script first to prepare the environment before
+building - it will use Homebrew to make sure Python is installed and
+up-to-date.
+
+    $ script/prepare-osx
+
+## Release process
+
+1. Open pull request that:
+ - Updates the version in `compose/__init__.py`
+ - Updates the binary URL in `docs/install.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 Create unpublished GitHub release with release notes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`.
+5. Publish GitHub release, creating tag
+6. Update website with `script/deploy-docs`
+7. Upload PyPi package
+
+        $ git checkout $VERSION
+        $ python setup.py sdist upload