Add comma placement checks
Add comma placement checks

Adds the following error codes:

C812	missing trailing comma
C813	missing trailing comma in Python 3
C814	missing trailing comma in Python 2
C815	missing trailing comma in Python 3.5+
C816	missing trailing comma in Python 3.6+
C818	trailing comma on bare tuple prohibited
C819	trailing comma prohibited

tvmaze/tvmaze