Add pygments and fonts

Dockerfile

@@ -35,7 +35,8 @@ RUN cpan YAML::Tiny
 RUN perl -MCPAN -e 'install "File::HomeDir"'
 
 RUN apt-get update -q \
-    && apt-get install -y git rubber python3-pip
+    && apt-get install -y --no-install-recommends \
+    rubber python3 python3-pip python3-pygments fonts-liberation fonts-font-awesome gsfonts
 RUN pip3 install gummi
 
 ENV HOME /workspace