Remove instructions on iptables

[nickjer]

I believe we should remove the step-by-step instructions on opening ports 80/443 using iptables as it can be insecure since the rules are inserted at the very top of the chain. Also the last command to save the new rules doesn't work on RHEL7.

Instead we should replace it with documentation such as:

https://wiki.centos.org/HowTos/Network/IPTables