Error response codes are ignored

[dhensby]

When the library sends the events to the server, if the server responds with an error status code (eg: 403) and the body cannot be parsed as expected (say because an HTML response is given), then the logger silently ignores the error and the log is treated as if it is successful.

I would suggest that error response status code like this should be dealt with as an error. Perhaps the retry logic can be short-circuited, but the error callbacks should be invoked so that the issue is not silently swallowed and ignored.