Merge pull request #42 from zlsh80826/dependabot/pip/nltk-3.6.6

Bump nltk from 3.4.5 to 3.6.6

Author: zlsh80826

requirements.txt

@@ -82,7 +82,7 @@ murmurhash==0.28.0
 natsort==5.3.3
 nbconvert==5.4.0
 nbformat==4.4.0
-nltk==3.4.5
+nltk==3.6.6
 nose==1.3.7
 notebook==5.7.8
 numpy==1.16.0