add Changelog file

Changelog.md

@@ -0,0 +1,21 @@
+# Changelog
+
+## v0.3.0 (05/16/2012)
+- support backends installed from npm
+- fix test suite failures
+
+## v0.2.1 (05/14/2012)
+- add graphite backend in debian packaging
+
+## v0.2.0 (05/04/2012)
+- support for pluggable backends
+
+## v0.1.1 (05/02/2012)
+- add gauges type
+- percentThreshold also accepts list of percentiles
+- base sampling on sampleRate
+- updates for debian packaging
+- client example updates
+
+## v0.1.0 (02/17/2012)
+- initial npm release