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`.