Reorganize mdv and observe packages

pkg/observe/lib/src/observable_box.dart

Index: pkg/observe/lib/src/observable_box.dart
diff --git a/pkg/mdv_observe/lib/src/observable_box.dart b/pkg/observe/lib/src/observable_box.dart
similarity index 73%
rename from pkg/mdv_observe/lib/src/observable_box.dart
rename to pkg/observe/lib/src/observable_box.dart
index 484a900f9b7faf66589114b91ef3b84c6ea0f318..7cc8fac5f325409fef30f85ca0157e4944aaac11 100644
--- a/pkg/mdv_observe/lib/src/observable_box.dart
+++ b/pkg/observe/lib/src/observable_box.dart
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-part of mdv_observe;
+part of observe;
 
 // TODO(jmesserly): should the property name be configurable?
 // That would be more convenient.
@@ -13,8 +13,6 @@ part of mdv_observe;
  * [ObservableMixin]. The property name for changes is "value".
  */
 class ObservableBox<T> extends ObservableBase {
-  static const _VALUE = const Symbol('value');
-
   T _value;
 
   ObservableBox([T initialValue]) : _value = initialValue;
@@ -22,16 +20,8 @@ class ObservableBox<T> extends ObservableBase {
   T get value => _value;
 
   void set value(T newValue) {
-    _value = notifyPropertyChange(_VALUE, _value, newValue);
+    _value = notifyPropertyChange(const Symbol('value'), _value, newValue);
   }
 
   String toString() => '#<$runtimeType value: $value>';
-
-  getValueWorkaround(key) {
-    if (key == _VALUE) return value;
-    return null;
-  }
-  void setValueWorkaround(key, newValue) {
-    if (key == _VALUE) value = newValue;
-  }
 }