Makes vagrant use hostname in config.yml.
Patches jenkins-job-builder::default to install argparse pkg.

Moves to using patched python and jenkins-job-builder cookbooks until
PRs accepted. jenkins-job-builder now installs argparse when only
python26 is available, so no need to install python27 from source.
Adds vagrant-cachier support.
Now gives databag users sudo privs via group rather than individually.