Update changelog

CHANGELOG.md

@@ -31,6 +31,7 @@ Example UDF config for a socket based UDF.
 - [#441](https://github.com/influxdata/kapacitor/issues/441): Fix panic in UDF code.
 - [#429](https://github.com/influxdata/kapacitor/issues/429): BREAKING: Change TICKscript parser to be left-associative on equal precedence operators. For example previously this statement `(1+2-3*4/5)` was evaluated as `(1+(2-(3*(4/5))))`
     which is not the typical/expected behavior. Now using left-associative parsing the statement is evaluated as `((1+2)-((3*4)/5))`.
+- [#456](https://github.com/influxdata/kapacitor/pull/456): Fixes Alerta integration to let server set status, fix `rawData` attribute and set default severity to `indeterminate`.
 
 ## v0.12.0 [2016-04-04]