Updates for Custom 404 pages, Safari's 304 blank-page error, robots.txt/humans.txt templates, and modified .htaccess 

While I was working on a website, I ran into a few issues, so I made a few changes to fix them before noticing that the changes I made had already been implemented, to a certain extent, on the Stacey project (after the fork to Cindy). I'm not sure if you're still developing Cindy, but I thought I'd give the pull request a shot.

Basically, the changes made are:

1. A workaround to prevent the Safari 304 blank-page bug (stacey.inc.php)
2. A fix to allow custom 404 pages to be used (stacey.inc.php)
3. Included templates for a robots.txt (and disallowing certain folders to be indexed) and humans.txt file
4. Slightly modified .htaccess file (disabled Directory Listing, enabled gzip compression, preventing .txt files in folders from being accessed)

Let me know what you think.