Release 0.4.0

```
Bob the Builder (1):
      Silvertip 0.3.6-SNAPSHOT

Jussi Virtanen (20):
      Handle NULL from 'ServerSocketChannel#accept'
      Clean up EventSource interface
      Use Server in ConnectionSendTest
      Remove 'Connection#accept'
      Use 'Connection#connect' in tests
      Remove 'Connection#attemptToConnect'
      Remove AbstractMessageParser
      Remove 'Events#dispatch'
      Remove 'Events#stop' and 'Events#isStopped'
      Do not rely on 'Callback#idle' in PingClient
      Do not rely on 'Callback#idle' in ConnectionSendTest
      Do not rely on 'Callback#idle' in ConnectionTest
      Remove 'Callback#idle'
      Remove 'EventSource#timeout'
      Clean up 'EventSource#register'
      Pass Events to 'EventSource#register'
      Optimize handling of closed connections
      Remove 'EventSource#unregister'
      Remove 'EventSource#isClosed'
      Do not synchronize 'Connection#txBuffers'

Pekka Enberg (8):
      Merge pull request #39 from valotrading/releases/0.3.5
      Fix API documentation in Events
      Merge pull request #41 from jvirtanen/fixes/non-blocking-accept
      Merge pull request #42 from jvirtanen/cleanups/event-source-interface
      Merge pull request #43 from jvirtanen/cleanups/connection-accept
      Merge pull request #44 from jvirtanen/cleanups/connection-attempt-to-connect
      Merge pull request #45 from jvirtanen/cleanups/abstract-message-parser
      Merge pull request #46 from jvirtanen/express
```