util: Add writefile_context to safely write files.
util: Add Python versions of the mutual information measures
cmty: Bugfix in cmty writing with mapping
sbmgraphs: add modularity fraction detectable functions
fixup! util: Add writefile_context to safely write files.
support/algorithms: g=None ability for CDMethod
support/algorithms: Make initial= argument work for Oslom and Louvain

- Louvain option still disabled since I'm not sure if it works.
support/algorithms: Fix up mainfunc some (remove interact)
test_commstats: More unit tests
nxutil: Add n_edges_subgraph function.
commstats.CmtyDensity: more efficient implementation
support/algorithms: Update docstrings for jako
support/algorithms.Infomap: rename args argument to _args
nxutil_c.pyx: Add file
Move all old C-depending code to old/
Minimal changes to make all code pass tests again
Further changes for old code migration
Merge branch 'move-old-code'
Move cmty similarity measures to pcd.cmtycmp
old/util.py: Fix In to return 1.0 for identical single communities