MAINT: add changelog entry for selection bugfix
- ``alt.SortField`` renamed to ``alt.EncodingSortField`` and ``alt.WindowSortField`` renamed to ``alt.SortField`` (https://github.com/vega/vega-lite/pull/3741)
+### Bug Fixes
+
+- Fixed serialization of logical operands on selections within
+ ``transform_filter()``: (#1075)
+
## Version 2.1.0 (Released June 6, 2018):
### Enhancements
