Add FAQ entry for "Buffering video, please wait" issue

[waldyrious]

I had the issue described in popcorn-time/popcorn-app#330 but in my case I has just accepted Windows' default settings in the firewall dialog (nw.exe allowed in private networks only). After seeing the discussion on that issue, and realizing the firewall settings I had picked could be the culprit, I went back to the Control Panel, found the firewall settings and edited them to allow nw.exe in public networks, and that made it work. It could be useful to have this info in the FAQ for others who may have just clicked OK in the firewall dialog, accepting the default firewall rules.

[ggonzaleza]

Also, perhaps a well written how-to-install guide could avoid this at all. :)

[waldyrious]

and illustrated :) I like dropbox's for instance.