Wrong owner and group of cache files #41
Description
In the same manner as in #37, when using vagrant and setting the composer_home to /home/vagrant/.composer, the cache files themselves (see the contents of /home/vagrant/.composer/cache) are created by root, meaning that if you once ran vagrant provision, you can't run composer update or install from inside the machine (sshing into the vagrant machine and running it from there) as a permissions issue will prevent you from updating the cache files.