GFA parsing fails with tags

[nrizzo]

compute_summary.py spits out an error if a GFA with S id seq LN:i:10 lines is given in input, because it does not seem to expect other fields after the sequence:

Traceback (most recent call last):
  File "compute_summary.py", line 361, in <module>
    compute_summary(parser.parse_args())
  File "compute_summary.py", line 237, in compute_summary
    vertex_labels, edges = load_graph(args.graph)
  File "compute_summary.py", line 18, in load_graph
    str_id, label = line[1:].strip().split()

[elarielcl]

Thank you for noting this!
Please take a look at #2