Fix php-cs-fixer not using tmp dir for cache (#16)

Author: ben-challis

.php-cs-fixer.php

@@ -139,6 +139,7 @@
     ])
     ->setRiskyAllowed(true)
     ->setUsingCache(true)
+    ->setCacheFile(__DIR__.'/tmp/.php-cs-fixer.cache')
     ->setIndent('    ')
     ->setLineEnding("\n")
     ->setFinder($finder);