Revert "bring CPANio::App::Document back in the main app"

This fixes the issue with the default fallback dispatcher returning 404:

    2014-08-16 #web-simple
    10:22 < BooK> ok, the issue is deeper than that: the dispatcher subs either returns a psgi app or nothing, but since my sub-apps are Web::Simple apps, they already are PSGI apps, so they HAVE to return a response, because as soon as they are entered, I'm out of the dispatcher
    16:25 < mst> BooK: oooh. and of course a Web::Simple app returns a 404 if not
    16:26 < mst> maybe overriding _build_final_dispatcher would make it not return a response?
    16:26 < mst> i.e.
    16:26 < mst> sub _build_final_dispatcher { undef }
    16:26 < mst> in the sub-application
    16:26 < BooK> mst: I tried something along those lines, but I think it doesn
    16:26 < BooK> 't work for the above reason
    16:27 < mst> err, the above reason doesn't make sense. a Plack app is just another thing to try, internally
    16:27 < mst> so if it returns nothing, dispatch should continue
    16:28 < BooK> I got some weird error, like "don't know how I got there"
    16:28 < BooK> possibly from plack
    16:28 < BooK> I'll try your version of _build_final_dispatcher
    16:28 < mst> that sounds like Web::Dispatch barfing
    16:29 < BooK> right now, I've worked around the issue, so I can ignore it during cpan day
    16:29 < mst> there's definitely code that does
    16:29 < mst> next unless @result and defined($result[0]);
    16:29 < mst> ooh. maybe 'undef' on its own works, but ... AHA
    16:29 < mst> sub _build_final_dispatcher { sub () {} }
    16:29 < mst> ^^ *that* should work
    16:30 < mst> that's clearly making life harder than it needs to be for sub-apps though
    16:30 < mst> I'll have to ponder how to make that not stupid

This reverts commit 5a3b9aa2309d7cce7a7cb86ed577254a1fc87365.