Adds basic sprite sheet support to sprites

sky/examples/game/lib/texture.dart

+part of sprites;
+
+class Texture {
+  final Image image;
+  Size _size;

[jackson, 2015/06/23 22:09:43]

You might want to make this public and final instead of private and having a
public getter

+  String _fileName;

[jackson, 2015/06/23 22:09:43]

Ditto

+  bool _rotated;

[jackson, 2015/06/23 22:09:43]

final?

+  bool _trimmed;

[jackson, 2015/06/23 22:09:43]

final?

+
+  Rect _frame;

[jackson, 2015/06/23 22:09:43]

Ditto

+  Rect _spriteSourceSize;

[jackson, 2015/06/23 22:09:43]

Ditto

+
+  Point _pivot;

[jackson, 2015/06/23 22:09:43]

final?

+
+  Texture(this.image) {
+    _size = new Size(image.width.toDouble(), image.height.toDouble());

[jackson, 2015/06/23 22:09:43]

Usually it's good to initialize members after the : and before the {} if you can

+    _trimmed = false;
+    _rotated = false;
+    _frame = new Rect.fromLTRB(0.0, 0.0, _size.width, _size.height);
+    _spriteSourceSize = new Rect.fromLTRB(0.0, 0.0, _size.width, _size.height);
+    _pivot = new Point(0.5, 0.5);
+  }
+
+  Texture._fromSpriteFrame(this.image, this._fileName, this._size, this._rotated, this._trimmed, this._frame,
+                           this._spriteSourceSize, this._pivot) {
+  }
+
+  Size get size => _size;
+
+  String get fileName => _fileName;
+
+  Rect get frame => _frame;
+
+  Rect get spriteSourceSize => _spriteSourceSize;
+
+  Texture textureFromRect(Rect rect, Point offset, bool rotated) {
+    // TODO: Implement this
+    return null;
+  }
+}