Log Message:
Update to 1.8.1

Upstream changes:
Networkx-1.8.1
Release date: 4 August 2013

Bugfix release for missing files in source packaging

Networkx-1.8
Release date: 28 July 2013

Highlights
Faster (linear-time) graphicality tests and Havel-Hakimi graph generators
Directed Laplacian matrix generator
Katz centrality algorithm
Functions to generate all simple paths
Improved shapefile reader
More flexible weighted projection of bipartite graphs
Faster topological sort, decendents and ancestors of DAGs
Scaling parameter for force-directed layout
Bug Fixes
Error with average weighted connectivity for digraphs, correct normalized \ 
laplacian with self-loops, load betweenness for single node graphs, isolated \ 
nodes missing from dfs/bfs trees, normalize HITS using l1, handle density of \ 
graphs with self loops
Cleaner handling of current figure status with Matplotlib, Pajek files now don't \ 
write troublesome header line, default alpha value for GEXF files, read curved \ 
edges from yEd GraphML