Add support for reverse proxys (#100)

getIP.php

@@ -1,4 +1,12 @@
 <?php
-header('Content-Type: text/plain; charset=utf-8');
-echo $_SERVER['REMOTE_ADDR'];
+    header('Content-Type: text/plain; charset=utf-8');
+    if (!empty($_SERVER['HTTP_CLIENT_IP'])) {
+        echo $_SERVER['HTTP_CLIENT_IP'];
+    } elseif (!empty($_SERVER['X-Real-IP'])) {
+        echo $_SERVER['X-Real-IP'];
+    } elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
+        echo $_SERVER['HTTP_X_FORWARDED_FOR'];
+    } else {
+        echo $_SERVER['REMOTE_ADDR'];
+    }
 ?>