added mkdir to spooler, and general config

when dealing with spoolers on cloud based ephemeral disks, or temporal disks like /dev/shm it's useful to to be able to ask uwsgi to create the directory before it adds the spooler. 

note: I use /dev/shm because due to PCI rules I can't write some of the spooler data to disk because it contains CVV/CID credit card data.