Improve Travis testing

- Added multiple versions of PostgreSQL to test (9.5, 9.6 and 10)
- Added multiple versions of Postgis to test
- Cleand travis yaml in favor of a script done in other project thanks
to Paul Ramsey

scripts/ci/install_postgres.sh

@@ -0,0 +1,38 @@
+#!/bin/bash
+
+# echo commands
+set -x
+
+# exit on error
+set -e
+
+dpkg -l | grep postgresql
+
+# Add the PDGD repository
+apt-key adv --keyserver keys.gnupg.net --recv-keys 7FCC7D46ACCC4CF8
+add-apt-repository "deb http://apt.postgresql.org/pub/repos/apt/ trusty-pgdg main"
+apt-get update
+
+# Remove those all PgSQL versions except the one we're testing
+PGSQL_VERSIONS=(9.2 9.3 9.4 9.5 9.6 10)
+/etc/init.d/postgresql stop # stop travis default instance
+for V in "${PGSQL_VERSIONS[@]}"; do
+    if [ "$V" != "$PGSQL_VERSION" ]; then
+        apt-get -y remove --purge postgresql-${V} postgresql-client-${V} postgresql-contrib-${V} postgresql-${V}-postgis-2.3-scripts
+    else
+        apt-get -y remove --purge postgresql-${V}-postgis-2.3-scripts
+    fi
+done
+
+apt-get -y autoremove
+
+# Install PostgreSQL
+apt-get -y install postgresql-${PGSQL_VERSION} postgresql-${PGSQL_VERSION}-postgis-${POSTGIS_VERSION} postgresql-server-dev-${PGSQL_VERSION}
+
+# Configure it to accept local connections from postgres
+echo -e "# TYPE  DATABASE        USER            ADDRESS                 METHOD \nlocal   all             postgres                                trust\nlocal   all             all                                     trust\nhost    all             all             127.0.0.1/32            trust" > /etc/postgresql/${PGSQL_VERSION}/main/pg_hba.conf
+
+# Restart PostgreSQL
+/etc/init.d/postgresql restart ${PGSQL_VERSION}
+
+dpkg -l | grep postgresql