Bighuge: Added the word "thesaurus" as a trigger.

Other changes:
- A simple `JSON.stringify(api_result).indexOf(mode) === -1` just won't
  do. It will fail if our search query was "related to nasty" because
  the JSON object would then contain the word "unpleasant." I'm sure Janet Jackson would agree: http://www.harkavagrant.com/index.php?id=347.

- The more trigger words we add, the more functions we would need (and
  these functions are global, too) because of the way the plugin was
  built. This version no longer creates multiple callback functions based on the trigger word.