Merge pull request #180 from ThomasCantonnet/finfo-bc-break

Fix BC break introduced by 3fc1e66

Author: weierophinney

src/File/MimeType.php

@@ -385,7 +385,7 @@ public function isValid($value, $file = null)
             $this->type = null;
             if (! empty($this->finfo)) {
                 $this->type = finfo_file($this->finfo, $file);
-                finfo_close($this->finfo);
+                unset($this->finfo);
             }
         }