Add .NET Standard 2.0 Preview

Author: terrajobst

roadmap.md

@@ -60,11 +60,12 @@ Core, and as always let us know what is important to you.
 
 ## Ship Dates
 
-| Milestone              | Release Date |
-|------------------------|--------------|
-| .NET Core 2.0 Preview  | Q2 2017  |
-| .NET Core 2.0          | Q3 2017  |
-| .NET Standard 2.0      | Q3 2017  |
+| Milestone                 | Release Date |
+|---------------------------|--------------|
+| .NET Core 2.0 Preview     | Q2 2017      |
+| .NET Standard 2.0 Preview | Q2 2017      |
+| .NET Core 2.0             | Q3 2017      |
+| .NET Standard 2.0         | Q3 2017      |
 
 # Components