Incorrect log statements

[chirag-manwani]

Summary

The log statements which notify state changes are not correct, there seems to be an issue with the (order of the) arguments passed to the notify function. Looks like the first argument being passed is self.

On this line, https://github.com/dream11/lua-circuit-breaker/blob/master/src/breaker.lua#L134, the notify function should be called like this
self.notify(cb_name, new_state)
Also, there should be a check if notify is nil or not since there is no default value.