Resource can now init with count = 0, without having to explicitly declare it anymore
Add validator for unique name among sibling nodes
Add spec files for models Node and Resource
Need to find root_id instead of hard-coding 1; create a root node if it's not there already; and remove 'add/remove_resource' actions
Root node might not have id=1, so check name instead
Add path to be able to require model files and reset db after each tests