Add two other references for captive portals. Fix #89.
Add two other references for captive portals. Fix #89.

ScheerMT/OS-X-Yosemite-Security-and-Privacy-Guide,DeadLion/macOS-Security-and-Privacy-Guide,drduh/OS-X-Yosemite-Security-and-Privacy-Guide,drduh/OS-X-Security-and-Privacy-Guide,drduh/macOS-Security-and-Privacy-Guide