early support for single archives — fix #853

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
conf.py.in

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
fix single-archives

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
create Nikola.posts, which contains paths to all posts (like Nikola.posts_per_*)

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
update CHANGES.txt to include notes about single archive support

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>