Merge branch 'fix_docker' into 'master'

Copy pgFormatter submodule in Dockerfile.

See merge request depesz/explain.depesz.com!16

docker/Dockerfile

@@ -20,6 +20,7 @@ RUN apt-get update && \
 
 RUN cpan install Pg::Explain
 COPY lib/ ./lib/
+COPY ext/ ./ext/
 RUN sed -i s/Mail::Sender/Email::Sender/g lib/Explain/Plugin/MailSender.pm
 COPY docker/explain.json explain.pl ./
 COPY layout/ /layout/