API updates

 * test passing: kicks clients that do not log in
 * index exports `Client` and `Server`
 * `createServer`: `options.keepAliveInterval` -> `options.kickTimeout`
 * `Client` event `end` includes `reason` argument
   - `LoginTimeout`
   - `KeepAliveTimeout`
   - `ServerShutdown`
 * `createClient`: Set `options.keepAlive` to `false` to disable sending
   keep alive packets
 * `Client`: `options.isServer` defaults to `false`.
add test, ping, and 2 API changes

 * passing test: responds to ping requests
 * `mc.ping` - ping a server for info
 * `createServer`: `options.timeout` -> `options.checkTimeoutInterval`
 * `Client` emits `connect` event