v2 / Tests: update Travis to 2.3.3 & 2.2.8.

Author: aseemk

.travis.yml

@@ -12,8 +12,8 @@ jdk:
 
 env:
   # test across multiple versions of Neo4j:
-  - NEO4J_VERSION="2.3.1"
-  - NEO4J_VERSION="2.2.7"
+  - NEO4J_VERSION="2.3.3"
+  - NEO4J_VERSION="2.2.8"
   - NEO4J_VERSION="2.1.8"
   - NEO4J_VERSION="2.0.4"