Minor fixes

monitor_thread: 
-Made code a bit easier to read by deleting one level
-changed `if comment.body[:15] == 'get_top_ten(me)':` to `if comment.body[:15] == 'get_top_ten(me)'.lower():` in case people mess up the capitalization

get_commentors: 
-took advantage of `submission.comments` only retrieving top level comments (unless you go into the `replys` part of the comment info)
-made the `redditor_list` a lot easier to understand

filter_words:
-super minor: check the O(1) before the O(n) function