Add if option to publicize

Publicize based on a conditional method passed as `if` in an options hash.
@ryanmuller This is kind of the meat of it.

If you would give this a shot locally on MM and do a code review, that'd be sweet. The easiest way to use locally is to go to MM Gemfile and `gem "rolypoly", path: "../rolypoly"` or whatever the path is for your setup.