Add Admin Notice for Conflicing Plugins & Themes

[robneu]

It might be worth adding an admin notice for any known plugin conflicts like other lightbox popups or anything that's known to cause a problem.

Obviously we should do what we can to mitigate as many conflicts as possible, but I don't really want to add a bunch of code overhead on the front end for dealing with these issues.

In cases where it doesn't make sense to work around an issue, it would be good to at least let people know why the plugin isn't working.

[robneu]

We haven't had enough reports of issues to justify this yet. Closing for now.