Use Postgres 9.4 on travis

.travis.yml

@@ -1,6 +1,6 @@
 language: rust
 addons:
-  postgresql: 9.3
+  postgresql: 9.4
 before_script:
 - "./.travis/setup.sh"
 script:

tests/types/mod.rs

@@ -146,7 +146,6 @@ fn test_json_params() {
 
 #[test]
 fn test_jsonb_params() {
-    if option_env!("TRAVIS").is_some() { return } // Travis doesn't have Postgres 9.4 yet
     test_type("JSONB", &[(Some(Json::from_str("[10, 11, 12]").unwrap()),
                           "'[10, 11, 12]'"),
                          (Some(Json::from_str("{\"f\": \"asd\"}").unwrap()),