Merge remote-tracking branch 'origin/master'

.dockerignore

+img_cache
+index
+slides
\ No newline at end of file

Dockerfile

@@ -7,7 +7,7 @@ RUN rm /etc/ImageMagick-6/policy.xml
 COPY policy.xml /etc/ImageMagick-6/policy.xml
 # Remove imagemagick policy from /etc/ImageMagick-6/policy.xml if pdf2img needed
 
-RUN mkdir app
+RUN mkdir app && mkdir app/slides && mkdir app/index && mkdir app/img_cache
 COPY . app
 WORKDIR app
 #RUN mkdir slides && mkdir index && mkdir img_cache