implement exports, fixes #141

test/codegen/expect/script.js

+#!/usr/bin/env iojs

[vsm, 2015/08/04 23:49:58]

cute :-)

Does this actually work?  I assume dart_library needs to be concatenated in
here?

[Jennifer Messerly, 2015/08/04 23:58:39]

yeah, it doesn't work yet :|

what we need here is module support, either ES6 or the nodejs `require` style.
If we did that transform then it would work:

#!/usr/bin/env iojs
let dart = require('dart_runtime/dart');
let core = require('dart/core');

// code here ...


ultimately covered by https://github.com/dart-lang/dev_compiler/issues/34

+dart_library.library('script', null, /* Imports */[
+  "dart_runtime/dart",
+  'dart/core'
+], /* Lazy imports */[
+], function(exports, dart, core) {
+  'use strict';
+  let dartx = dart.dartx;
+  function main(args) {
+    let name = args[dartx.join](' ');
+    if (name == '')
+      name = 'world';
+    core.print(`hello ${name}`);
+  }
+  dart.fn(main, dart.void, [core.List$(core.String)]);
+  // Exports:
+  exports.main = main;
+});