Added a generalized Article class.
Merge branch 'master' of https://github.com/gt-big-data/retina-crawler

Conflicts:
	CrawlerRunners.py
Merge branch 'master' of https://github.com/gt-big-data/retina-crawler

Conflicts:
	CrawlerRunners.py
Merge branch 'master' of https://github.com/gt-big-data/retina-crawler

Conflicts:
	writers.py
Article class created and working with SimpleCrawlers.