Fix to follow PEP8

Fixed by using autopep8: `autopep8 --in-place --aggressive
pagerank_alg.py`. Looks like it mainly fixed spaces around operators,
and the use of two spaces before a comment.
Minor fixes in the docstrings
autopep8 on tests/test_pagerank.py
Add dangling_edge parameter to google_matrix
Fix import ordering
Add spaces to some multiline strings
Add a test for dangling nodes
Implement and test dangling nodes for pagerank
Handle dangling nodes in pagerank_scipy
Delete unnecessary normalization
Variable name improvements
Rework dangling nodes and personlization approach

Modify dangling nodes and persionalization pieces of the pagerank algorithm.
Change name from dangling_edges to dangling.
Force node ordering if not specified in nodelist argument to be G.nodes().
Merge pull request #1 from hagberg/thenovices-pagerank

Rework dangling nodes and personlization approach
Minor fixes; Fix bug in scipy routine
Always use 'N' for the number of nodes
Fix pep8 errors
Having dangling vector default to the personalization vector
Avoid dict comprehension to support Python 2.5
Clean up the power iteration loop slightly
Switch from xrange to range for Python 3 support

Obviously range() is not ideal for Python 2, but usually max_iter will be
small enough that it shouldn't be a problem. If needed itertools.repeat can be
used.