Skip jsonb test on Travis

Author: sfackler

tests/types/mod.rs

@@ -146,6 +146,7 @@ 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()),