experiment with assign attribute to graphs using node df
basic structure of create_graph and updated read_networkplan
fixed fake node finding issue.  can find disconnected subgraphs now
finished root_id and experimented dom tree
sketched out algo for creating directed trees from connected and disconnected graphs
further experiment with separate & union, seems that the nominal vertex name is preserved but the actual vertex name will be reordered
quick hack to fix directed_subgraph creating function
 'the above' works now! please review my comment and change the change if needed
Fixed bug (attributes were not being carried through properly) via graph.disjoint.union
cleanup
Merge pull request #18 from SEL-Columbia/create_graph

Create graph