added trend filter and evaluation method

Changed parseTwitter to filter out tweets with > 2 trending topics (in
addition to target hashtag)

Added evaluation code to show our recall
removed print statement
fixed tweet duplication
fixed number of filtered tweets
Test for module 1 and 2.
Added switched for stemming.
Don't return the segmentation of a hashtag if there's not any real segments.
removed tweet links
updated retrieveTweetText to remove emoticons

retrieveTweetText(hashtag, hundredsOfTweets=2, filterEmoticons = 0):

set filterEmoticons to be 1
updated retrieveTweetText filters
Added a parameter of search category, Web/News.
Merge branch 'master' of github.com:mzweilin/HashTag-Understanding
added retrieveRelatedHashtags method
added caseSensitive param for retrieveTweetText()
stopwords
Merge branch 'master' of github.com:mzweilin/HashTag-Understanding
Correctly remove stopwords.
Added a switch for segmentation.
Replaced total term frequency with document frequency.
Added interface of n-gram threshold.