Generators: always present docs in alphabetical order

As things were, the order in which sniff documentation was presented was dependent on the file system the sniffs were found on.

Fixed now by making the order logical and consistent.

src/Generators/Generator.php

@@ -60,6 +60,9 @@ public function __construct(Ruleset $ruleset)
             }
         }
 
+        // Always present the docs in a consistent alphabetical order.
+        sort($this->docFiles, (SORT_NATURAL | SORT_FLAG_CASE));
+
     }//end __construct()