Merge pull request #1 from Gummibeer/patch-2

add getBoxSize() as abstract method

src/Intervention/Image/AbstractFont.php

@@ -63,6 +63,13 @@ abstract class AbstractFont
      */
     abstract public function applyToImage(Image $image, $posx = 0, $posy = 0);
     
+    /**
+     * Calculates bounding box of current font setting
+     *
+     * @return array
+     */
+    abstract public function getBoxSize();
+
     /**
      * Create a new instance of Font
      *