ADD: backend node attribute model
ADD: backend API for attributes
FIX: back/front-end connection with node attributes
ADD: create and node attributes from a node
ADD: delete node attribute button
FIX: node binding in node attributes controller
ADD: delete attributes when node is deleted
ADD: add attributes only when the node is not new
Merge pull request #5 from fespinoza/attributes

Add Attributes to Nodes (Actors and Relations)