Bug fixes and updates in backbone_wu

[anaston]

Hi there, great tool!:) I spotted a few small issues with backbone_wu, added/changed some functionality (see verbosity and avgdeg) and refactored bits of the code to make it easier to follow using numpy functionality. I added specific commits for each change and I also left some comments below. Let me know if you are happy with the changes or whether I should revise some bits. Cheers, Agoston