add travis build matrix for all built-in PostgreSQL versions

.travis.yml

@@ -8,7 +8,9 @@ php:
 
 env:
   - DB=mysql
-  - DB=pgsql
+  - DB=pgsql POSTGRESQL_VERSION=9.1
+  - DB=pgsql POSTGRESQL_VERSION=9.2
+  - DB=pgsql POSTGRESQL_VERSION=9.3
   - DB=sqlite
   - DB=mysqli
 
@@ -17,6 +19,7 @@ before_script:
   - sh -c "if [ '$DB' = 'pgsql' ]; then psql -c 'DROP DATABASE IF EXISTS doctrine_tests_tmp;' -U postgres; fi"
   - sh -c "if [ '$DB' = 'pgsql' ]; then psql -c 'create database doctrine_tests;' -U postgres; fi"
   - sh -c "if [ '$DB' = 'pgsql' ]; then psql -c 'create database doctrine_tests_tmp;' -U postgres; fi"
+  - sh -c "if [ '$DB' = 'pgsql' ]; then sudo service postgresql stop; sudo service postgresql start $POSTGRESQL_VERSION; fi"
   - sh -c "if [ '$DB' = 'mysql' ]; then mysql -e 'create database IF NOT EXISTS doctrine_tests_tmp;create database IF NOT EXISTS doctrine_tests;'; fi"
   - sh -c "if [ '$DB' = 'mysqli' ]; then mysql -e 'create database IF NOT EXISTS doctrine_tests_tmp;create database IF NOT EXISTS doctrine_tests;'; fi"
   - composer --prefer-source --dev install