Integrated 'Natural' node package
Added Tweet object

- created unit test
- created the basic tweet object, with id, text, stemmedWords,
date, favoritesCount, and retweetCount
Added 4 datasets to help with testing
Fix basic tweet object

- fixed construct and minimun word length
- fixed unit test
Removed useless Article object
Added keyWords object to compute main keywords in a dataset
First method to merge keywords

- added useless keywords dictionary
Added topics in the home controller
Merge branch 'feature/backend-algo'