Add comment formatter.

[iandunn]

See #8

[iandunn]

This doesn't fully resolve #8 entirely, since it only supports comment_author_email. I don't personally feel like comment author names qualify as sensitive. That could always be added as a future iteration, though.

[iandunn]

@ivankruchkoff , do you have any thoughts on this and #12?

[ivankruchkoff]

I think this is a good start and can be added in for other fields comment_content, comment_approved (random between yes and no), comment_post_ID etc

Would also be nice for

wp ha -f comments.comment_author_email=random

and

wp ha -f comments.comment_author_email=random

to function identical to

wp ha -f posts.post_title=random,posts.post_content=markov