Notify User if the talk page exists

Upon typing a title, the plugin will check for the main page, the talk
page, a draft page in the format 'draft:title' and the talk page for the
draft, in that order of importance

Known issues: The error message flashes a little when the name is being
typed, due to the different namespaces being checked.

http://www.google-melange.com/gci/task/view/google/gci2014/5877487489777664
https://github.com/WPAFC/afch-rewrite/issues/26
We don't really need to run ALL of those checks -- that is, title blacklist as well as protection levels -- for any pages other than the mainspace page. Reason being, the *reason* we check protection/title blacklist is because these factors can prevent the reviewer from accepting the article (because they would be unable to move the page to its new official title, since said title would be blacklisted).

In other words, there's not really any need to check if the Draft talk page or the article talk page are blacklisted/protected. We're better off just doing a simple existence check for these two pages, and showing a *non-blocking* alert message if they do exist (you'll note that in the current function, the submit button is disabled if the title already exists). The button probably should not be disabled in the case of any already-existent draft talk/talk page, because there are certainly reasons to accept even if they do exist.

I hope this makes sense! I will be on IRC tomorrow afternoon your time if you'd like to talk then!