Test parity: match default test using latest stable version

.travis.yml

@@ -19,6 +19,10 @@ env:
 
 matrix:
   include:
+    - php: 5.6
+      env: WP_VERSION=4.6.1 WP_MULTISITE=0
+    - php: 7.0
+      env: WP_VERSION=4.6.1 WP_MULTISITE=0
     - php: 5.6
       env: WP_VERSION=4.6.1 WP_MULTISITE=1
     - php: 7.0