Merge pull request #34 from jwsy/master

Update Chapter5.ipynb. Thanks @jwsy!
Update README.md
Update README.md
Update README.md
Merge pull request #37 from jwsy/master

Config updates for nltk, IPython run as root again
Moved OAuth discussion out of main Facebook (Chapter2) notebook and moved it into a new AppendixB notebook instead. Will do the same with LinkedIn soon. Chapters will be kept simple and as lightweight as possible with OAuth being an important detail to be included in supporting material
Adding note about D3 force directed visualization in notebook
Moving LinkedIn OAuth 2.0 details from Chapter3 to _AppendixB. Updating VM config to use a fork of python-linkedin for the time being to simplify the login flow for Chapter3. Smoothing out a few more code issues in Chapter3
Smoothing out some minor issues with how examples in the notebook and book don't align
More tweaks to example layout to better align with the text of the book
Fixing misnumbered example
Removal of unnecessary unicode in caption