Fetch Articles, Count Terms, Generate Incoming Nodes

1. create_500mb_test.py -> gives back 50000 articles.
Warning: still has scaling issues (will need to do in 100
article chunks, or so).  Test on smaller dataset
2. count_terms -> Goes throuhg all articles within xml file
and creates frequency count of all links
3. generate_incoming_nodes -> Goes through all articles
and generates mapping from outcoming node to incoming node
(opposite of what we previously had)