cache dirs not created properly

[jxstanford]

First, great project. It got me up and running very quickly! Along the way I ran into two small issues. The aptcache and pipcache folders did not exist, so there were a couple dead links during the stack.sh run. I resolved this by issuing the following commands and rerunning stack.sh:

mkdir /home/vagrant/cache/aptcache
mkdir /home/vagrant/cache/pipcache

Cheers,
John