[travis] Update postgres & postgis

Author: nemesifier

.travis.yml

@@ -1,7 +1,12 @@
+dist: trusty
 sudo: false
 language: python
 cache: pip
-
+addons:
+  postgresql: "9.3"
+  apt:
+    packages:
+      - postgresql-9.3-postgis-2.3
 services:
   - postgresql