completed documentation

README.md

@@ -11,6 +11,16 @@ This role installs, enables and configures the PHP module `pdo`. It is the base
     * This option specifies the PDO config file for a database driver.
   * default: ""
 
+* php_mod_pdo_name
+  * description:
+    * This option specifies the name of a PDO module.
+  * default: ""
+
+* php_mod_pdo_priority
+  * description:
+    * This option specifies the priority of a PDO module.
+  * default: ""
+
 * php_mod_pdo_dns_aliases
   * description:
     * This option contains a list of dictionaries with PDO aliases.