Adds Flask app for tree map visualization

* has different root from word cloud visualization (/treemap)
* loads as separate app file (treemap.py)
Adds initial work on generating category tree.
Parses category tree and maps businesses to categories.
Merge branch 'treemap'

Conflicts:
	category_tree/category.json
	category_tree/category_tree.py
	category_tree/yelp/category.py