Update README.md

Added details regarding the two runtime assemblies.

Author: wiredwiz

README.md

@@ -2,6 +2,8 @@
 
 A set of tools written in C# for testing Antlr4 generated C# grammar assemblies. 
 These tools are meant to supplement the need to continually test with the Antlr java TestRig assembly.
+Currently the tool only supports the Antlr4.Runtime assembly, but a 2.0 release with support for the standard runtime assembly is forthcoming (and overdue).
+In the future I will work on a version that supports both dynamically, but the current design of the app makes this impossible.
 
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