message: Update readme-facebook.md
  Fixed a typo.
diff: @@ -30,7 +30,7 @@ Table of Contents
  Copy this token, you'll need it!
  -4) Define your own "verify token" - this a string that you control that Facebook will use to verify your web hook endpoint.
  +4) Define your own "verify token" - this is a string that you control that Facebook will use to verify your web hook endpoint.
  5) Run the example bot app, using the two tokens you just created. If you are _not_ running your bot at a public, SSL-enabled internet address, use the --lt option and note the URL it gives you.
  