adding dispersion as a centrality measure
updated dispersion to use built in nx methods and set comprehension
incorporating dschult set method suggestions... with significant increase in speed
refactored to allow optional u, v... added suggestions for normalizations...
good thing we do tests
clean .gitignore and tests bug
correcting dict comprehension in tests....
"fixing docstring"
Merge branch 'master' into dispersion
Remove unused math directive in docstring.
Updating dispersion docstring.
Adding dispersion to reference documentation.