install deb provided by pandoc maintainer

Dockerfile

@@ -11,6 +11,7 @@ MAINTAINER Netlify
 ENV LANGUAGE en_US:en
 ENV LANG en_US.UTF-8
 ENV LC_ALL en_US.UTF-8
+ENV PANDOC_VERSION 2.2.1
 
 # language export needed for ondrej/php PPA https://github.com/oerdnj/deb.sury.org/issues/56
 RUN export DEBIAN_FRONTEND=noninteractive && \
@@ -131,7 +132,6 @@ RUN export DEBIAN_FRONTEND=noninteractive && \
         nasm \
         openjdk-8-jdk \
         optipng \
-        pandoc \
         php5.6 \
         php5.6-xml \
         php5.6-mbstring \
@@ -170,6 +170,12 @@ RUN wget -nv https://github.com/wkhtmltopdf/wkhtmltopdf/releases/download/0.12.4
     cp -r ./ /usr/ && \
     wkhtmltopdf -V
 
+# install Pandoc (more recent version to what is provided in Ubuntu 14.04)
+RUN wget https://github.com/jgm/pandoc/releases/download/$PANDOC_VERSION/pandoc-$PANDOC_VERSION-1-amd64.deb && \
+    dpkg -i pandoc-$PANDOC_VERSION-1-amd64.deb && \
+    rm pandoc-$PANDOC_VERSION-1-amd64.deb && \
+    pandoc -v
+
 ################################################################################
 #
 # Libvips