You need to have ssl (https) enabled. I tried the 000webhost free hosting before, sadly it doesn't come with ssl. Thats something you have to pay for. Also they are crazy slow. For fb apps you actually have to shell out some cash at some point. Its for security reasons for devs, fb, and the users. There is currently no reasonably cheap or free way to get it. Self signing doesn't work either.
sorry I can't post full links yet...
You can try: heroku (dot) com/pricing Free to sign up and I think your first Dyno(server) is free.
Check: developers (dot) facebook (dot) c0m/blog/post/558/ for more info on how to set that up with them.