randomise temp directory name to avoid collisions

Author: troosan

src/PhpWord/Writer/AbstractWriter.php

@@ -216,7 +216,7 @@ public function setTempDir($value)
     protected function getTempFile($filename)
     {
         // Temporary directory
-        $this->setTempDir(Settings::getTempDir() . '/PHPWordWriter/');
+        $this->setTempDir(Settings::getTempDir() . uniqid('/PHPWordWriter_'). '/');
 
         // Temporary file
         $this->originalFilename = $filename;