added stopwatch example

added requestAnimationFrame polyfill

moved raf logic into a subscription

separated logic into multiple files, all state lives in a global namespaced model, reset no longer sends multiple actions only one

examples/stopwatch/client.js

@@ -0,0 +1,15 @@
+const choo = require('../../')
+
+const stopwatch = require('./models/stopwatch')
+const mainView = require('./views/main')
+
+const app = choo()
+
+app.model(stopwatch)
+
+app.router((route) => [
+  route('/', mainView)
+])
+
+const tree = app.start()
+document.body.appendChild(tree)