Deprecate create_degree_sequence.
Add some line (di)graph literature references.
Generate random node indices instead of calling random.choice.
Remove non-ascii hyphen from references. Set file encoding.
Merge pull request #941 from hagberg/gexf-long

Use long type for GEXF with Python2 long or Python3 int.

Fixes #940
Merge pull request #944 from hagberg/multigraph-operators

Multigraph operators
BUG: fix test_read_LEDA on windows.
Merge pull request #945 from hagberg/deprecate-degseq

Deprecate create_degree_sequence.
Fixes #863
Merge pull request #934 from jtorrents/est-avg-clust-coeff

Add approximation for average clustering coefficient
Rename trees->tree
Handle corner cases.

Simplify logic using not_implemented_for()
Recognize pointless concept
Rename tree_recognition->recognition
Add docs
Make helper line graph functions explicitly private.
Add comment about line graph requiring sortable nodes in G.
Merge pull request #937 from chebee7i/linegraph

Update line graph algorithm to handle self-loops correctly
Fix incorrect reference to function name.
Use io.BytesIO() instead of temporary file
Merge pull request #812 from chebee7i/pydot

Drawing with pydot/Graphviz and inline IPython displays.
Revert "Merge pull request #812 from chebee7i/pydot". Addresses #812.

This reverts commit e736d4b4db44f45c59039d44f92013748cbef3f4, reversing
changes made to ceb31d0f4f14556d4e804868efd23c11f2e6b776.
Merge pull request #950 from chebee7i/revert_812

Revert "Merge pull request #812 from chebee7i/pydot". Addresses #812.