Rename klass variable to callback
Rename klass variable to callback

klass is not a Class-like object, it's an instance of one of the incoming message classes. I couldn't find a better name than the ones used in the Messenger Platform documentation.

Naming is hard.
jgorset/facebook-messenger,hyperoslo/facebook-messenger,jgorset/facebook-messenger,hyperoslo/facebook-messenger,stamm/facebook-messenger,stamm/facebook-messenger