Looks like PHP7 is deprecating some of the usages CMS Made Simple uses in development.ADOConnection has a deprecated constructor in phar://C:/wamp64/www/cmsms/cmsms-2.1.2-install.php/lib/adodb_lite/adodb.inc.php on line 183
If you run into this issue, I found that switching over to PHP5 fixed the problem and allowed me to proceed with the installation.