Add v0.4.0 changelog

Author: clue

CHANGELOG.md

@@ -4,6 +4,27 @@ This file is a manually maintained list of changes for each release. Feel free
 to add your changes here when sending pull requests. Also send corrections if
 you spot any mistakes.
 
+## 0.4.0 (2014-08-xx)
+
+* BC break: The `Client` class has been renamed to `StreamingClient`.
+  Added new `Client` interface.
+  (#18 and #19)
+
+* BC break: Rename `message` event to `data`.
+  (#21)
+
+* BC break: The `Factory` now accepts a `LoopInterface` as first argument.
+  (#22)
+
+* Fix: The `close` event will be emitted once when invoking the `Client::close()`
+  method or when the underlying stream closes.
+  (#20)
+
+* Refactored code, improved testability, extended test suite and better code coverage.
+  (#11, #18 and #20)
+
+> Note: This is an intermediary release to ease upgrading to the imminent v0.5 release.
+
 ## 0.3.0 (2014-05-31)
 
 * First tagged release