Don't copy subgraphs in cuthill_mckee_ordering().

The connected_component_subgraphs() function used in the cuthill_mckee_ordering() makes a copy.  That causes new node objects to be created which might not be desirable when returning a node ordering if the hash changes when a new object is created. Fix by not copying nodes when forming a subgraph of connected nodes.
Adjacency list format write adds extra delimiter

Remove trailing delimiter from write_adjlist().  Fixes bug of adding an extra anonymous node when reading back file written with write_adjlist()
Add delimiter test for multiline_adjlist format
Whitespace cleanup
Whitespace cleanup
Don't modify input list in _all() operators.
Check for dot_parser to catch error importing pydot
Whitespace cleanup/formatting
Merge pull request #905 from hagberg/pydot-test

Pydot test fixes
Add config file for https://travis-ci.org
Update travis.ci config
Update travis.ci config
Fix tests for cuts.
Fix example for random_bipartite

The check of a connected graph doesn't play any role in the example.
Very rarely it gave an error to nosetests.
Add pypy test to travis-ci
Merge pull request #906 from dschult/cuttestfixes

Fix some tests and examples that sometimes failed
Add some extra packages in travis-ci test config
Merge branch 'master' of github.com:networkx/networkx
Adjust travis-ci config
Add more packages to travis-ci config