Fixed ClassCastException in org.vertx.java.busmods.BusModBase.getOptionalLongConfig()

<a href="https://github.com/vert-x/vert.x/issues/494">Issue #494</a> - when deploying a module with config containing a <code>Long</code> value which is less than MAXINT, reading the value from within the module fails with <code>ClassCastException</code>.