Support for PG11

- Start using Docker to test in TravisCI
- Support for PG10 and PG11 and remove support for old versions

scripts/ci/docker-test.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+docker run -e PGHOST=localhost -e PGPORT=5432 -v `pwd`:/srv --entrypoint="/bin/bash" ${1} /srv/scripts/ci/run_tests_docker.sh && \
+    docker ps --filter status=dead --filter status=exited -aq | xargs docker rm -v

scripts/ci/run_tests_docker.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+/etc/init.d/postgresql start
+
+cd /srv
+
+make clean-all
+make install
+
+cd /srv/src/pg
+
+make test || { cat /srv/src/pg/test/regression.diffs; false; }