Update changelog

Author: lukewaite

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Release Notes for `logstash-input-cloudwatch_logs`
 
+## v1.0.0 Pre-Release (2017-06-24)
+* BREAKING CHANGE: `log_group` must now be an array, adds support for specifying multiple groups or prefixes
+* Refactored ingestion, fixes multiple memory leaks (Fixes [#24](https://github.com/lukewaite/logstash-input-cloudwatch-logs/issues/4))
+* Pull only log_events since last ingestion (Fixes [#10](https://github.com/lukewaite/logstash-input-cloudwatch-logs/issues/10))
+* Incrementally write to since_db on each page of data from the CWL API (Fixes [#4](https://github.com/lukewaite/logstash-input-cloudwatch-logs/issues/4))
+
 ## v0.10.3  (2017-05-07)
 
 ### Fixed