added message to changelog about increased minimal node version

Author: unclechu

CHANGELOG.md

@@ -5,7 +5,9 @@ v0.4.1
 ------
 
 - Removed test code from <b>npm</b> package
-  ([see pull request #21](https://github.com/unclechu/node-deep-extend/pull/21)).
+  ([see pull request #21](https://github.com/unclechu/node-deep-extend/pull/21));
+- Increased minimal version of Node from 0.4.0 to 0.12.0
+  (because can't run tests on lesser version anyway).
 
 v0.4.0
 ------