Config updates for nltk, IPython run as root again

1. Removed most uses of sudo (#35) in bootstrap.sh but needed to upgrade pip as sudo or else the pip command wouldn't be found.
2. Changed bootstrap.sh so that ipython would be run as root again
2. Added inline downloads for nltk packages in Chapters 4 & 5 with nltk.download('maxent_treebank_pos_tagger')