add toAscii method to Italian Internet provider

This was inspired by issue #189. Copied and adapted from French Internet provider. Even if current Person provider for Italian does not contains any accented letters, I added them anyway, for forward compatibility. The only current issue with Italian Person provider are names with accent inside, that currently are translated into invalid email, like "ld'amico@yahoo.com"

src/Faker/Provider/it_IT/Internet.php

@@ -6,4 +6,17 @@ class Internet extends \Faker\Provider\Internet
 {
     protected static $freeEmailDomain = array('gmail.com', 'yahoo.com', 'hotmail.com', 'email.it', 'libero.it', 'yahoo.it');
     protected static $tld = array('com', 'com', 'com', 'net', 'org', 'it', 'it', 'it');
+
+    /**
+     * Converts Italian characters to their ASCII representation
+     *
+     * @return string
+     */
+    private static function toAscii($string)
+    {
+        $from = array('à', 'À', 'é', 'É', 'è', 'È', 'ù', 'Ù', "'");
+        $to   = array('a', 'A', 'e', 'E', 'e', 'E', 'u', 'U', '');
+
+        return str_replace($from, $to, $string);
+    }
 }