Created the FiltratorInterface in preparation of using the library in…

… the \Sirius\Forms library

src/Filtration/Filtrator.php

@@ -3,7 +3,7 @@
 
 use Sirius\Filtration\Utils;
 
-class Filtrator
+class Filtrator implements FiltratorInterface
 {
     // selector to specify that the filter is applied to the entire data set
     const SELECTOR_ROOT = '/';

src/Filtration/FiltratorInterface.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace Sirius\Filtration;
+
+interface FiltratorInterface {
+
+    function add($selector, $callbackOrFilterName = null, $options = null, $recursive = false, $priority = 0);
+
+    function remove($selector, $callbackOrName = true);
+
+    function filter($data = array());
+}