feat: add PostgreSQL 9.4 to .travis.yml matrix

Add PostgreSQL 9.4 to matrix of JDK/databases that are tested against.

Author: sehrope

.travis.yml

@@ -44,3 +44,15 @@ matrix:
     - jdk: oraclejdk8
       addons:
         postgresql: "9.3"
+    - jdk: openjdk6
+      addons:
+        postgresql: "9.4"
+    - jdk: openjdk7
+      addons:
+        postgresql: "9.4"
+    - jdk: oraclejdk7
+      addons:
+        postgresql: "9.4"
+    - jdk: oraclejdk8
+      addons:
+        postgresql: "9.4"