v 0.0.1,  - initial release

v 0.0.2, 27/12/2012 - examples for nickel module

v 0.0.3, 22/12/2012 - python 2.6 compatibility fix

v 0.0.4, 29/01/2013 - accessors to Edge and GraphState classes added

v 0.0.5  07/02/2013 - draw.py fixed to work with old version of pydot
                    - tests moved to the folder with file tested

v 0.0.6  01/06/2013 - draw_directed.py - example script to draw graphs from
                      graph_state notation (only fields printed on graph)
                    - different_ext_legs.py - example that shows how to mark
                      some ext legs with graph_state

v 1.0.0  04/09/2014 - completely refactored. Added arbitrary properties
                      for lines or vertices. Added fabrique to produce
                      GraphState instances

v 1.0.1  14/09/2014 - no additional dependencies

v 1.0.2  22/02/2015 - added doc strings
