Layouts with duplicate identifiers allowed

[denisdefreyne]

It is possible to have layouts/weblog/author/index.html and layouts/weblog/author.html, even though those resolve into the same identifier.

This is something that nanoc should not allow, since it is pretty much always an error.

CC @jugglinmike — I believe this is causing the problem you’ve been having.

[denisdefreyne]

I was convinced nanoc checks that, but apparently it does not.

[denisdefreyne]

@jugglinmike I can make no guarantees that this solves the problem, but it is a step in the right direction :)

[denisdefreyne]

Fixed by #435.