fixed digital ocean Vagrantfile

The current digital ocean Vagrantfile didn't work for me. I updated it and ran the phpunit tests and everything still passes. However, I was unable to actually create a manifest and test it with digital ocean locally. I attempted both the quickstart and just cloning the app. I got PuPHPet running but every time i tried to create "Create My Manifest!" i got the following: 

( ! ) Warning: filemtime(): stat failed for /tmp/5237df48ef15d8N7TML.zip in /var/www/puphpet.dev/src/Puphpet/Controller/Front.php on line 106
Call Stack
-#	Time	Memory	Function	Location
1	0.0012	292448	{main}( )	../index.php:0
2	0.4098	2569888	Silex\Application->run( )	../index.php:6
3	0.4387	3035120	Silex\Application->handle( )	../Application.php:481
4	0.4515	3131256	Symfony\Component\HttpKernel\HttpKernel->handle( )	../Application.php:504
5	0.4515	3131320	Symfony\Component\HttpKernel\HttpKernel->handleRaw( )	../HttpKernel.php:73
6	0.4877	3336688	call_user_func_array ( )	../HttpKernel.php:129
7	0.4877	3337112	Puphpet\Controller\Front->createAction( )	../HttpKernel.php:129
8	4.5453	6871056	filemtime ( )	../Front.php:106