Bump release
Update reease values for 1.8rc1
Update latest to point to new docs
Add tag to make gh-pages

Now use make tag=networkx-x.x gh-pages to build tagged documentation.
The default is development.
Use git@github instead of https
Update README year
Merge pull request #917 from hagberg/master

Update README year
Update documentation (overdue) to reflect move to github
Add release date
Merge pull request #909 from hagberg/update-release-1.8

Update release 1.8
Set release to networkx-1.8
Bump release to networkx-1.9dev