Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Fix. parse_edgelist documentation

Changes:
- fix mixing result+params
- added missing ``lines`` param
- use same order of params as in signature
Merge pull request #1109 from lukmdo/fix_doc_parse_edgelist

Fix. parse_edgelist documentation
Fix bug that capacity_scaling does not saturate negative selfloops
Fix python2.6 compatibility
Remove JSON serializer helpers

This complexity isn't really needed.  You can simply write

>>> import json
>>> s = json.dumps(json_graph.node_link_data(G))
Reduce constant factor in BinaryHeap
Merge pull request #1115 from ysitu/capacity_scaling

Fix bug that capacity_scaling does not saturate negative selfloops
Merge pull request #1114 from hagberg/remove-json-helper

Remove json helper
Add source root directory to sys.path in Sphinx conf.py
Enable Sphinx MathJax extension

The official MathJax HTTPS CDN is used.
Merge pull request #1121 from ysitu/doc

Add source directory to sys.path and enable MathJax in conf.py