adding game_of_life sample

dart/samples/webcomponents/game_of_life/README.md

+Conway's Game of Life
+=====================
+
+This package contains a reusable Game of Life widget built using Dart web
+components. Here's a rundown of what's here:
+
+  `componenets/`  contains the web components used to build the game
+  `test/` contains unit tests
+  `index.html`, `game_of_life.dart` are a sample app consisting of exactly one
+      Game of Life widget and nothing else.
+
+Compiling and Running
+---------------------
+
+To use these components, or to compile the sample app, you must have the
+experimental version of dart2js with no-wrapper web components support. You can
+get it at `https://github.com/samhopkins/bleeding_edge`. Then to compile the
+sample, run
+  
+  `dart2js game_of_life.dart -ogame_of_life.js`
+
+and open `index.html` in a browser.
+
+To use the Game of Life component in your app, import
+`components/components.dart`.
+
+Running the Tests
+-----------------
+
+We cannot presently use the usual test infrastructure in the repo, since it does
+not play well with pub right now. To run the tests, first compile them with
+
+  `dart2js tests/game_of_life_tests.dart -o tests/game_of_life_tests.js`.
+
+Then open `tests/test_page.html` in your browser.