Use different exception for Invalid API key or access token

[gocebonev]

For better exception handling it would be nice to have a different exception thrown when the Api Key or access token are invalid instead of a generic all purpose ApiException.

[elzozo13]

Wouldn't this be fixed by this pr (#133)? Would not be a different exception but you would have a reliable code; imo that should suffice in like 90% of the cases.