Adding couscous build for docs 1.5

Dockerfile

@@ -0,0 +1,30 @@
+FROM composer as build-couscous
+
+RUN curl -OS http://couscous.io/couscous.phar
+RUN chmod +x couscous.phar
+RUN mv couscous.phar /usr/local/bin/couscous
+
+COPY . /app
+WORKDIR /app
+RUN cd 1.5 && couscous generate
+
+FROM python:alpine as build-stage
+
+# Set up workspace and install mkdocs and dependencies.
+COPY . /app
+WORKDIR /app
+RUN pip install -r requirements.txt && rm -rf $HOME/.cache/pip
+
+RUN cd 3.0 && mkdocs build
+RUN cd 2.0 && mkdocs build
+
+FROM nginx:1.13.12-alpine as production-stage
+
+COPY --from=build-stage /app/3.0/site/ /usr/share/nginx/html/3.0
+COPY --from=build-stage /app/2.0/site/ /usr/share/nginx/html/2.0
+COPY --from=build-couscous /app/1.5/.couscous/generated /usr/share/nginx/html/1.5
+
+RUN echo "<meta http-equiv=\"refresh\" content=\"0; url=/3.0/\">" > /usr/share/nginx/html/index.html;
+RUN chown -R nginx:nginx /usr/share/nginx/html/
+EXPOSE 80
+CMD ["nginx", "-g", "daemon off;"]