choo components (#639)

* add components

* example: componentize header

* fix choo SSR

* example: componentize footer

* example: fix footer

* update component cache asserts

* componentize todos

* reorder example dir

* fix example tests

* fix dep check test

* Add garbage collection of unused components

* Apply args when calling identity

* update to new component preview

* update nanocomponent

* fix cache err name

* remove static methods from example

* restore app.emit() function

* public API tests

* offset component cache iteration by 2

* whitelist contents of component folder (#643)

* allow lru number arg

* fix lint typo

example/components/info.js

@@ -0,0 +1,16 @@
+var Component = require('../../component')
+var html = require('bel')
+
+module.exports = class Info extends Component {
+  update () {
+    return false
+  }
+
+  createElement () {
+    return html`<footer class="info">
+      <p>Double-click to edit a todo</p>
+      <p>choo by <a href="https://yoshuawuyts.com/">Yoshua Wuyts</a></p>
+      <p>Created by <a href="http://shuheikagawa.com">Shuhei Kagawa</a></p>
+    </footer>`
+  }
+}