Do not take failures as successes due to "diff" command succeeding

Also check which versions of postgresql are installed, to drop 9.1

.travis.yml

@@ -1,9 +1,10 @@
 before_install:
   - sudo apt-get install -q postgresql-server-dev-9.3
   - sudo apt-get install -q postgresql-9.3-postgis-2.1
+  - dpkg -l | grep postgresql
   - # Install schema_triggers
   - hg clone https://bitbucket.org/malloclabs/pg_schema_triggers &&
     cd pg_schema_triggers && make && sudo make install && cd -
 
 script:
-  - make installcheck || cat regression.diffs
+  - make installcheck || { cat regression.diffs; false; }