Created Lurk class

Created Lurk object, the main object that reads the configuration, creates the trackers, the scraper and maintain the queue and cache.
Extended parsers

Now raw_html parser is also created
Tracker abstraction

Now the tracker has a parser and a trigger objects assigned.
Changed some options for testing purposes

Single file option activated, and keyword added for testing using a test thread.
Now a config file stores sticky posts for each board

A config file that will be updated by Lurk, stores how many posts are sticky posts on each board, to remove them from scraping.
Added scrapers module

Added scrapper selector, scrapper abstract class and an implementation for 4chan.
Added triggers module

Added trigger selector, trigger abstract class and a default keyword-based trigger.