added use line for filesystem

Author: Richard Hoogstad

src/Dflydev/Pimple/Provider/DoctrineOrm/DoctrineOrmServiceProvider.php

@@ -14,6 +14,7 @@
 use Doctrine\Common\Cache\ApcCache;
 use Doctrine\Common\Cache\ArrayCache;
 use Doctrine\Common\Cache\CacheProvider;
+use Doctrine\Common\Cache\FilesystemCache;
 use Doctrine\Common\Cache\MemcacheCache;
 use Doctrine\Common\Cache\MemcachedCache;
 use Doctrine\Common\Cache\XcacheCache;