Standardise getenv call for EMAIL

If sending an array of $to, the getenv check would potentially fail, in Linux, due to being case sensitive.

Resolves #5

classes/postal.php

@@ -57,7 +57,7 @@ public static function send($subject, $body, $to, $to_name = '', $from = null, $
                 if (\Fuel::$env != \Fuel::DEVELOPMENT) {
                     $message->to($ar_to_name.' <'.$ar_to_email.'>');
                 } else {
-                    $env = getenv('email');
+                    $env = getenv('EMAIL');
                     if (!$env) {
                         $env = 'root@localhost';
                     }