Add a minimum php requarament

Author: wojsmol

features/scaffold-theme-tests.feature

@@ -8,7 +8,7 @@ Feature: Scaffold theme unit tests
     When I run `wp theme path`
     Then save STDOUT as {THEME_DIR}
 
-  @less-than-php-7.2
+  @require-php-5.6 @less-than-php-7.2
   Scenario: Scaffold theme tests
     When I run `wp scaffold theme-tests p2child`
     Then STDOUT should not be empty