feat(electron): complete electron integration

* chore(package): update webpack to beta.22

Lastest version before breaking changes.

* feat(electron): Complete Electron integration.

New task to build targeting Electron:

    "build:electron": Alias for build:electron.full
    "prebuild:electron.full": "npm run clean:electron",
    "build:electron.full": "npm run build:electron.renderer && npm run build:electron.main",
    "postbuild:electron.full": "npm run electron:start",

    "build:electron.renderer": Webpack aplication with production properties and targeting electron-renderer
    "build:electron.main": Webpack main Electron with production properties and targeting electron

    "electron:start": "electron build"

config/electron/webpack.renderer.common.js

@@ -0,0 +1,67 @@
+const helpers = require('./../helpers');
+const webpack = require('webpack');
+
+const METADATA = {
+  baseUrl: './',
+  ENV: 'renderer',
+};
+
+/*
+ * Webpack configuration
+ *
+ * See: http://webpack.github.io/docs/configuration.html#cli
+ */
+module.exports = function (env) {
+  METADATA.ENV = env
+    ? env
+    : METADATA.ENV
+
+  return {
+
+    /*
+    * Static metadata for index.html
+    *
+    * See: (custom attribute)
+    */
+    metadata: METADATA,
+
+    /**
+     * The plataform target where the aplication is going to run in.
+     * It support target electron-renderer, but is not documented.
+     *
+     * See: https://webpack.github.io/docs/configuration.html#target
+     */
+
+    target: 'electron-renderer',
+
+    /**
+     * Options affecting the output of the compilation.
+     *
+     * See: http://webpack.github.io/docs/configuration.html#output
+     */
+    output: {
+
+      /**
+       * The output directory as absolute path (required).
+       *
+       * See: http://webpack.github.io/docs/configuration.html#output-path
+       */
+      path: helpers.root('build'),
+    },
+
+    /*
+    * Include polyfills or mocks for various node stuff
+    * Description: Node configuration
+    *
+    * See: https://webpack.github.io/docs/configuration.html#node
+    */
+    node: {
+      global: 'window',
+      crypto: 'empty',
+      process: true,
+      module: false,
+      clearImmediate: false,
+      setImmediate: false
+    }
+  };
+};