fix: hadolint fixes (DL3018, DL3013, quoted strings)

Dockerfile

@@ -1,30 +1,30 @@
-FROM "python:3.7-alpine"
+FROM python:3.7-alpine
 
 ARG BUILD_DATE
 ARG VCS_REF
 ARG VERSION
 
+# hadolint ignore=DL3018
 RUN apk --no-cache add --virtual build-dependencies \
         build-base libffi-dev libressl-dev && \
+    # hadolint ignore=DL3013
     pip install --no-cache-dir ansible-review && \
     apk del build-dependencies
 
-LABEL "maintainer"="dockerimages@cabillot.eu" \
-      "org.label-schema.name"="ansible-review" \
-      "org.label-schema.base-image.name"="docker.io/library/python" \
-      "org.label-schema.base-image.version"="3.7-alpine" \
-      "org.label-schema.description"="Ansible-review in a container" \
-      "org.label-schema.url"="https://github.com/willthames/ansible-review" \
-      "org.label-schema.vcs-url"="https://gitlab.cabillot.eu/jcabillot/ansible-review/" \
-      "org.label-schema.vendor"="Julien Cabillot" \
-      "org.label-schema.schema-version"="1.0" \
-      "org.label-schema.applications.ansiblelint.version"="latest" \
-      "org.label-schema.vcs-ref"="$VCS_REF" \
-      "org.label-schema.version"="$VERSION" \
-      "org.label-schema.build-date"="$BUILD_DATE" \
-      "org.label-schema.usage"="docker run --rm -v $(pwd):/data registry.cabillot.eu/jcabillot/ansible-review -p ."
-# TODO: fix this last line
+LABEL maintainer="dockerimages@cabillot.eu" \
+      org.label-schema.name="ansible-review" \
+      org.label-schema.base-image.name="docker.io/library/python" \
+      org.label-schema.base-image.version="3.7-alpine" \
+      org.label-schema.description="Ansible-review in a container" \
+      org.label-schema.url="https://github.com/willthames/ansible-review" \
+      org.label-schema.vcs-url="https://gitlab.cabillot.eu/jcabillot/ansible-review/" \
+      org.label-schema.vendor="Julien Cabillot" \
+      org.label-schema.schema-version="1.0" \
+      org.label-schema.applications.ansiblelint.version="latest" \
+      org.label-schema.vcs-ref="$VCS_REF" \
+      org.label-schema.version="$VERSION" \
+      org.label-schema.build-date="$BUILD_DATE" \
+      org.label-schema.usage="docker run --rm -v $(pwd):/data registry.cabillot.eu/jcabillot/ansible-review -p ."
 
 ENTRYPOINT [ "/usr/local/bin/ansible-review" ]
-CMD [ "--help" ]
-# TOREAD: https://gist.github.com/paul-butcher/7bab39b85abc9c7334df02004cba2eb3
+CMD [ "--help" ]