Merge pull request #33 from sharelatex/bg-add-docker-file-for-image-conversions

add dockerfile to install packages needed by filestore

services/filestore/Dockerfile

@@ -0,0 +1,5 @@
+FROM node:6.9.5
+
+RUN apt-get update
+# we also need imagemagick but it is already in the node docker image
+RUN apt-get install -y --no-install-recommends ghostscript optipng