Add today's date to the changelog

Author: DustinCampbell

CHANGELOG.md

@@ -3,7 +3,7 @@
 * When opening a .csproj-based .NET Core project in VS Code, the C# extension will not activate until a C# file is opened in the editor. ([#1150](https://github.com/OmniSharp/omnisharp-vscode/issues/1150))
 * There currently is no completion support for package references in csproj files. ([#1156](https://github.com/OmniSharp/omnisharp-vscode/issues/1156))
 
-## 1.9.0
+## 1.9.0 (April 20, 2017)
 
 #### Unit Testing