Allow relative path in autoconfigure

[budde377]

When passing a relative path to api.autoconfigure() (e.g. autoconfigure('../chef-repo')) it will wrongly change convert the relative path, of the client-key, to a absolute path.

For instance: When calling autoconfigure('../chef-repo') where chef-repo contains .chef/client.pem file and configuration file .chef/knife.rb containing the line:

client_key               "#{current_dir}/client.pem"

the path of the client key will be changed from the correct relative path: ../chef-repo/.chef/client.pem to the wrong /some/abs/path/chef-repo/chef-repo/.chef/client.pem which should be /some/abs/path/chef-repo/.chef/client.pem.

This happens because of a wrong assumption at https://github.com/coderanger/pychef/blob/master/chef/api.py#L130

Tested on version 0.2.3.

Please let me know if I should create a pull-request.

[gliptak]

On a related node, is there a way to get a user friendly message when the autoconfigure() returned None (was unsuccessful)? Thanks