Revert "We can now choose whether future-dated posts are published by default with a configuration variable. We still see all posts in preview mode."

This reverts commit 4b9b499251ea4d613f7bd6f3b0500c6485c5ec21.

I did this because Brandon Mathis decided to implement this feature
differently in his commit 38353f216cb90454adb3c1f0b44521f0a8bf9394.
Avoid nasty surprises when deploying to a server west of you.

Creating a new post with the rake task now includes the time zone offset
so that when you write a post in GMT +2, then deploy it to your
production server in GMT −7, you don’t scratch your head wondering what
happened to your post.

Unfortunately, it might still happen that your file is named one day
differently than your post’s creation instant. I didn’t want to try to
fiddle with that. This seems to work well enough.