Replicating LaurentLuce tutorial using hashtags. Works as far as extract_features.

In extract_features:
Passed in the result of getting all hashtags from timeline as HASHTAGS, used a test list of hashtags (["tcot", "p2", "Maddow"]) as hashtags.
Function returned a dictionary of hashtags from HASHTAGS list paired with True or False. "Maddow" was True.
WIP. Marking point at which I will change Chris' suggestion that extract_hashtags add to a set called HASHTAGS.

extract_hashtags adds to a set called HASHTAGS defined in main(). It works - creates a set (all unique items) of all hashtags from a given timeline.
Ignore storage() function; training_set is not working.
However, I need to change this; making it a set too early precludes using FreqDist to get the frequency of different hashtags.