Update CHANGELOG for v1.0.2-preview-015

Author: nfbot

CHANGELOG.md

@@ -1,8 +1,7 @@
 # Change Log
 
-## [**Changes available only in 'Preview' NuGet packages:**](https://github.com/nanoframework/lib-nanoFramework.Networking.Sntp/tree/HEAD)
-
-[Full Changelog](https://github.com/nanoframework/lib-nanoFramework.Networking.Sntp/compare/v1.0.2-preview-005...HEAD)
+## [v1.0.2-preview-012](https://github.com/nanoframework/lib-nanoFramework.Networking.Sntp/tree/v1.0.2-preview-012) (2018-11-19)
+[Full Changelog](https://github.com/nanoframework/lib-nanoFramework.Networking.Sntp/compare/v1.0.2-preview-005...v1.0.2-preview-012)
 
 **Documentation and other chores:**