Ignores role & environment attributes when using Chef 11

[tomdz]

In Chef 11, the handling of node attributes vs. role/environment default_attributes/override_attributes has changed (http://www.opscode.com/blog/2013/02/05/chef-11-in-depth-attributes-changes/). More specifically, it looks like the attributes methods on the node called by the bag_config library (https://github.com/hw-cookbooks/bag_config/blob/master/libraries/bag_config.rb#L114-120) don't include the environment and role defaults/overrides (https://github.com/opscode/chef/blob/master/lib/chef/node/attribute.rb#L150-177).
In effect this means that default_attributes/override_attributes in roles & environments are currently ignored when using bag_config.