Django Dockerfile typo

Firstly, thanks for the great tutorial.

While reading the blog and code here, I found some inconsistence in [django-on-docker/deployment-project/djangoproject/Dockerfile](https://github.com/hedonhermdev/django-on-docker/blob/master/deployment-project/djangoproject/Dockerfile) , and that might be some typos.

At the very first code version in your blog, the env args are
```
# These two environment variables prevent __pycache__/ files.
ENV PYTHONUNBUFFERED 1
ENV PYTHONDONTWRITEBYTECODE 1
```
, but in the end of the blog and in this repo, the env args are
```
ENV PYTHONBUFFERED 1
ENV PYTHONWRITEBYTECODE 1
```
, and only the first form can be found in the python document.