Add simple unit tests for node/network_util.py

o Clean up node/network_util.py spacing and imports
o Add run_tests.sh that will discover the python unit tests and run them. This
  could be expanded to run the behave tests in the future.
o Add *.swp to .gitignore
Merge pull request #100 from julianknutsen/test-network-util

Add simple unit tests for node/network_util.py