Add Webpack Hotloading

By using `webpack-dev-server --config app/assets/webpack.config.js --progress --inline --module-bind --hot`
you should now be able to take advantage of hot loading, i.e. you
should notice that changing your client_application.cjsx will cause
the page to reload. When using React components, they should simply
reload without a full page refresh

DevProcfile

@@ -1,2 +1,2 @@
 web: rails s
-webpack: webpack-dev-server --config app/assets/webpack.config.js --progress --inline
+webpack: webpack-dev-server --config app/assets/webpack.config.js --progress --inline --module-bind --hot

app/assets/package.json

@@ -5,7 +5,7 @@
   "devDependencies": {
     "webpack": "~1.4.13",
     "webpack-dev-server": "*",
-    "react-hot-loader": "0.5.0",
+    "react-hot-loader": "*",
     "jsx-loader": "*",
     "css-loader": "*",
     "expose-loader": "~0.6.0",

app/assets/webpack.config.js

@@ -9,6 +9,7 @@ module.exports = {
   entry: {
     App: [
       'webpack-dev-server/client?http://localhost:8080/assets/',
+      'webpack/hot/only-dev-server',
       './javascripts/client_application.cjsx'
     ]
   },