never type for token

also got rid of `NearleyToken` interface because it is no longer
referenced with `never` for the type

lib/generate.js

@@ -193,16 +193,11 @@
         output += parser.customTokens.map(function (token) { return "declare var " + token + ": any;\n" }).join("")
         output += parser.body.join('\n');
         output += "\n";
-        output += "interface NearleyToken {\n";
-        output += "  value: any;\n";
-        output += "  [key: string]: any;\n";
-        output += "};\n";
-        output += "\n";
         output += "interface NearleyLexer {\n";
         output += "  reset: (chunk: string, info: any) => void;\n";
         output += "  next: () => NearleyToken | undefined;\n";
         output += "  save: () => any;\n";
-        output += "  formatError: (token: NearleyToken) => string;\n";
+        output += "  formatError: (token: never) => string;\n";
         output += "  has: (tokenType: string) => boolean;\n";
         output += "};\n";
         output += "\n";