feat(transpiler): Transform for..of to Dart as for..in

fixes #53

modules/facade/src/collection.dart

@@ -1,8 +1,35 @@
 library facade.collection;
 
-import 'dart:collection' show HashMap;
+import 'dart:collection' show HashMap, IterableBase, Iterator;
 export 'dart:core' show Map, List, Set;
 
+class MapIterator extends Iterator<List> {
+  Iterator _iterator;
+  Map _map;
+
+  MapIterator(Map map) {
+    this._map = map;
+    this._iterator = map.keys.iterator;
+  }
+  bool moveNext() {
+    return this._iterator.moveNext();
+  }
+  List get current {
+    return this._iterator.current != null ?
+      [this._iterator.current, this._map[this._iterator.current]] :
+      null;
+  }
+}
+
+class IterableMap extends IterableBase<List> {
+  Map _map;
+
+  IterableMap(Map map) {
+    this._map = map;
+  }
+  Iterator<List> get iterator => new MapIterator(this._map);
+}
+
 class MapWrapper {
   static HashMap create() => new HashMap();
   static HashMap createFromStringMap(m) => m;
@@ -21,6 +48,7 @@ class MapWrapper {
   static int size(m) {return m.length;}
   static void delete(m, k) { m.remove(k); }
   static void clear(m) { m.clear(); }
+  static Iterable iterable(m) { return new IterableMap(m); }
 }
 
 // TODO: how to export StringMap=Map as a type?

modules/facade/src/collection.es6

@@ -23,6 +23,7 @@ export class MapWrapper {
   static size(m) {return m.size;}
   static delete(m, k) { m.delete(k); }
   static clear(m) { m.clear(); }
+  static iterable(m) { return m; }
 }
 
 // TODO: cannot export StringMap as a type as Dart does not support renaming types...