Add an example of the skip_existing argument to the comment stream docs
Add an example of the skip_existing argument to the comment stream docs

There's a question every other week in /r/redditdev about how to skip existing comments in a stream since people don't know to check the streamgenerator docs.
praw-dev/praw,leviroth/praw,praw-dev/praw,13steinj/praw,gschizas/praw,gschizas/praw,13steinj/praw,leviroth/praw