Do not run berks-api as root.

Use chpst to set the user to node[:berkshelf_api][:owner]
in the berks-api runit run script.
Have the app recipe create the user before it's home directory.

This resolves the issue of having to converge the node twice
to pick up the directory owner/group permissions.
Merge pull request #149 from thorduri/master

Make it possible to run it out the box as the berkshelf user.