In your new cops installation does the file ./cops/vendor/autoload.php exist or not?
Edit: I was able to verify your error by deliberately downloading the zip with (only) source code and not doing (in a terminal, in your case directed to /Applications/Abyss Web Server/htdocs/cops) :
Code:
wget https://getcomposer.org/composer.phar
php composer.phar global require "fxp/composer-asset-plugin:~1.1"
php composer.phar install --no-dev --optimize-autoloader
You should copy these lines one at a time into the terminal [then <enter>]

then do your usual things and it should work.
You can also download this zip
https://github.com/seblucas/cops/rel...cops-1.1.1.zip and then unzip it into a ./cops directory. This should work.
If not let me know and I will try to help you.