add single files, secure server, hello world

single_file_tests/print_env.dart

@@ -0,0 +1,10 @@
+#!/usr/bin/env dart
+
+import 'dart:io' show Platform;
+
+main() {
+  Map<String, String> envVars = Platform.environment;
+  envVars.forEach((k, v) => {
+    print('$k = $v')
+  });
+}