[change] export or replace react-dom methods

This change adds the react-dom methods to the main export, since this is
a Web-only environment (React Native does something similar). It
augments the default render methods in order to move style sheet
management under the control of the library (necessary for
code-splitting support).

Relates to #52

examples/index.html

@@ -2,7 +2,5 @@
 <meta charset="utf-8">
 <title>React Native for Web</title>
 <meta name="viewport" content="width=device-width, initial-scale=1">
-<meta name="description" content="The core React Native components adapted and expanded upon for the web">
-<style id="react-stylesheet"></style>
 <div id="react-root"></div>
 <script src="/examples.js"></script>