Switched nested attribute character to '.' so '_' is valid in an attribute
knife-psearch v0.0.3

- Use . rather than _ to denote subkeys.
Rely on chef_server_url as search_url has been removed. Reference CHEF-4388.
Merge branch 'fix-config-ref' of https://github.com/mdkent/knife-psearch into mdkent-fix-config-ref