Update CHANGELOG.md

Author: arl

CHANGELOG.md

@@ -45,7 +45,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Remove datadog-specific code from [general] section. Instead add [metrics] which can be extended with baker.MetricsClient interfaces. [#34](https://github.com/AdRoll/baker/pull/34)
 - Remove duration parameter from baker.Main [#62](https://github.com/AdRoll/baker/pull/62)
 - TimestampRange filter accepts 'now' as range [#106](https://github.com/AdRoll/baker/pull/106)
-- standardize the components' structs names [#105](https://github.com/AdRoll/baker/pull/105)
+- Standardize the components' structs names [#105](https://github.com/AdRoll/baker/pull/105)
+- **Breaking** Change func FieldName to FieldNames (slice) as it allows to know the number of defined fields [#110](https://github.com/AdRoll/baker/pull/110)
 
 ### Removed