Darwin, theres no missing setup/requirements file. The one you have is probably from the develop branch you tried out. Yes the
should load the setup/requirements.php file if TastyIgniter hasn't been setup yet, but that was the case before it was changed in version 1.4.2 i think.
The case now is instead of looking for a setup/requirements.php file, it looks for a requirements() function in the setup/controller/Setup.php file, which exists. The requirements() loads the setup/views/requirements.php view file.
The common issue for the 404 error page or blank page will be file permissions, mod_rewrite, so i'd suggest checking this. Or its probably related to the Ngnix or web server error?