Hashtag Processing

I was having trouble installing some of the extra stuff, so I made an
extra file to do the hashtag stuff. As of right now it has two
functions: hashtag_list returns a list of all of the hashtags in
tweetSubset and hashtag_count(hashtags) takes in the list of hashtags
and reads through tweetSubset again and returns a list of lists, each of
which contains the tweet and a 0 or 1 for each hashtag in hashtags