Docs: Show currently supported TypeScript version (eslint#157)

Author: JamesHenry

README.md

@@ -4,6 +4,12 @@ A parser that converts TypeScript into an [ESTree](https://github.com/estree/est
 
 **Important:** This parser is still in the very early stages and is considered experimental. There are likely a lot of bugs. You should not rely on this in a production environment yet.
 
+## Supported TypeScript Version
+
+The version of TypeScript supported by this parser is `2.0.x`. Please ensure that you are using this version before submitting any issues.
+
+Due to a bug in the TypeScript Compiler it was not possible to officially support TypeScript `2.1.x`, please see this issue for more details on using `2.1.x`: https://github.com/eslint/typescript-eslint-parser/issues/149
+
 ## Usage
 
 Install: