Berksfile support for temporary directory sync

Hi,

There was an bug in berksfile support in case you used a directory outside of kitchen. In that case it would not work. Please merge this fix to get it working. 
Problem here is this:

cookbook_path is an array of local (to kitchen) directories which are uploaded to a server with ./ prefix. 

env.cookbook_search_paths should be an array of any directories which needs to be uploaded to a server e.g. berks_directory in /tmp/bers. If I put everything to cookbook_paths I have no way how to distinguish them.