added nodal roles

participation coef and within module degree, with weighted graph
functionality.
Update nodal_roles.py
chaged import on weighted_modularity, cleaned up nodal_roles
cleaned up nodal_roles, added tests
cleaned up nodal_roles
cleaned up nodal_roles
cleaned up nodal_roles
cleaned up nodal_roles within community degree, runs fast
cleaned up nodal_roles,added option for nans or infinity numbers
nodal roles done
nodal roles docs cleaned up
nodal roles docs cleaned up,working on tests
good array of tests now in place
speed up tests, made explicit communities
good array of tests now in place
Merge pull request #21 from mb3152/master

Add nodal roles for weighted partitions from @mb3152