Update changelog

CHANGELOG.md

@@ -8,10 +8,21 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Added
+
+- Add the `ReadOnlySpan` and `ReadWriteSpan` interfaces to provide better control for accessing span data. (#1360)
+
 ### Changed
 
 - Move the OpenCensus example into `example` directory. (#1359)
 - `NewExporter` and `Start` functions in `go.opentelemetry.io/otel/exporters/otlp` now receive `context.Context` as a first parameter. (#1357)
+- Rename `export.SpanData` to `export.SpanSnapshot` and use it only for exporting spans. (#1360)
+- Store the parent's full `SpanContext` rather than just its span ID in the `span` struct. (#1360)
+- Improve span duration accuracy. (#1360)
+
+### Removed
+
+- Remove `errUninitializedSpan` as its only usage is now obsolete. (#1360)
 
 ## [0.14.0] - 2020-11-19