Allow for comments when creating/updating reviews

[ppfeister]

fbrnch should allow for additional comments to be added when creating or updating reviews on bz. Sometimes it's necessary to add some notes, and this would avoid the additional step of going to bz to send another email, when it can be just the one post.

Maybe a --comment/-c flag on each subcommand. When provided with a string, append that comment. Otherwise, open $EDITOR to modify the bz message before sending.