Upgrade 'websocket-client' and 'http-kit' Dependencies.

`[org.eclipse.jetty.websocket/websocket-client "9.3.0.M0"]` contains a fix for [this bug](https://bugs.eclipse.org/bugs/show_bug.cgi?id=444748) and `WebSocketClient` objects now get garbage collected. See the behaviour when opening/closing a few thousand sockets in quick succession:

![image](https://cloud.githubusercontent.com/assets/198072/4466956/5e1a9c18-48ea-11e4-86e0-d3c8df57de59.png)

Previously:

![image](https://cloud.githubusercontent.com/assets/198072/4466999/fed39718-48ea-11e4-8f6f-29c5bebf7057.png)