Allowed IP feature for checking ips (check.php)

You can now add allowed IPs to $allowedIPs in Experiment/Settings.php.
Any IPs added here willpass any eligibility checks. Make sure that you
leave in the "::1" as it will allow multiple attempts when working
locally.
Merge pull request #4 from adamblake/checkphp

Allowed IP feature for checking ips (check.php)