Final QA updates (#386)

Author: gahjelle

docker-continuous-integration/web/Dockerfile

@@ -43,8 +43,7 @@ ENV PATH="$VIRTUALENV/bin:$PATH"
 COPY --from=builder /home/realpython/dist/page_tracker*.whl /home/realpython
 
 RUN python -m pip install --upgrade pip setuptools && \
-    python -m pip install --no-cache-dir page_tracker*.whl && \
-    rm -rf page_tracker*.whl
+    python -m pip install --no-cache-dir page_tracker*.whl
 
 CMD ["flask", "--app", "page_tracker.app", "run", \
-     "--host", "0.0.0.0", "--port", "5000"]
+    "--host", "0.0.0.0", "--port", "5000"]