Saving stable version
Creating id_type for Arcs (its own address) and id attribute. Adding copy/move constructors.
Correcting minor typo when printing flux
Id is not a template parameter any more
Adding Adjacency_list_traits and using CRTP to create adjacency list internal types. Overloading functions to internal representation
beg and end are now just ids. Still need changes to adapt to new Adjacency_list
No needed now
Updating library header
Making fields beg and end be modifiable
Adding functions to remove arcs and vertexes