Added Excel2007 support && fixes issue SpartnerNL#22

Author: Patrick Brouwers

src/Maatwebsite/Excel/Excel.php

@@ -904,6 +904,10 @@ private function decodeFormat($ext = false)
                 return 'Excel5';
                 break;
 
+             case 'xlsx':
+                return 'Excel2007';
+            break;
+
             case 'csv':
                 return 'CSV';
                 break;
@@ -935,10 +939,6 @@ public function setFreeze($pane = 'A2')
         return $this;
     }
 
-
-
-
-
     /**
      * Freeze the first row
      * @return  $this