Allow "True" and "False" as gexf bools.
Merge pull request #971 from chebee7i/gexf

"convert_bool" in gexf.py does not handle all bools
Fix bug in gml writer

Remove unneeded extra recursive call to listify.
It added an extra set of double quotes.
Merge pull request #981 from hagberg/gml-nested

Fix bug in gml writer
Graph initialisation support for tuple edge-lists
Merge pull request #984 from ninjin/tuple-init

Graph Initialisation Support for Tuple Edge-lists
Make coveralls work again.