Remove packetIndexes dependency in client.js

[rom1504]

https://github.com/PrismarineJS/node-minecraft-protocol/blob/master/src/client.js#L37

The packetIndexes.packetStates[direction].hasOwnProperty(event) check can just be removed. It doesn't matter if some non-packet events are added to the packetToParse object. There's basically just 'error' and 'session'.

Getting rid of the dependency in client.js will make things easier for cross version work by limiting the reading of packets definitions to serializer.js

[rom1504]

Would be possible to use https://nodejs.org/api/events.html#events_emitter_listenercount_type there.
But it's only available in node 4.0 (see nodejs/node#734 ) so I guess not.