Upgrade to Silvertip 0.4.1

Silvertip 0.4.1 contains significant changes compared to the previous versions:

- The `Events#dispatch` method is removed. The control of the event loop is maintained in the application, which must call repeatedly `Events#process` or `Events#processNow'`.

- The `Callback#idle` method is removed. Keep-alives and such must be handled in the application between calls to `Events#process` or `Events#processNow`.

- The `Events#stop` and `Events#isStopped` methods are removed, and the `Events#close` method is added.