[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

config/webpack.config.js

@@ -7,7 +7,8 @@ module.exports = {
   },
   externals: [{
     'react': true,
-    'react-dom': true
+    'react-dom': true,
+    'react-dom/server': true
   }],
   output: {
     filename: 'react-native-web.js',