Dockerfile fix user and dirs permissions

Dockerfile

@@ -8,8 +8,11 @@ RUN pip install -r requirements/base.txt -r requirements/production.txt
 
 COPY . .
 
-RUN useradd app
-RUN chown -R app /app
+RUN bash -c 'adduser --disabled-login --quiet --gecos app app &&  \
+             chmod -R o+r /app/ && \
+             mkdir /app/media_files && \
+             chown -R app:app /app/media_files && \
+             chmod o+x /app/run.sh'
 USER app
 
 # TODO HACK!