Update inflection from 0.4.0 to 0.5.0

requirements.txt

@@ -2,7 +2,7 @@ Click==7.1.2
 click-default-group==1.2.2
 contextlib2==0.6.0.post1
 future==0.18.2
-inflection==0.4.0
+inflection==0.5.0
 isodate==0.6.0
 lxml==4.5.1
 markdown==3.1.1 # pyup: >=3.1,<3.2 # 3.2 drops Python 2.7 support