Properly note when 0.5.0 features were released

[ci skip]

docs/deployment/dockerfiles.md

@@ -42,13 +42,15 @@ Setting `$DOKKU_DOCKERFILE_CACHE_BUILD` to `true` or `false` will enable or disa
 
 ### Procfiles and Multiple Processes
 
+> New as of 0.5.0
+
 You can also customize the run command using a `Procfile`, much like you would on Heroku or
 with a buildpack deployed app. The `Procfile` should contain one or more lines defining [process
 types and associated commands](https://devcenter.heroku.com/articles/procfile#declaring-process-types).
 When you deploy your app a Docker image will be built, the `Procfile` will be extracted from the image
 (it must be in the folder defined in your `Dockerfile` as `WORKDIR` or `/app`) and the commands
 in it will be passed to `docker run` to start your process(es). Here's an example `Procfile`:
- 
+
 ```
 web: bin/run-prod.sh
 worker: bin/run-worker.sh