Remove extra JS output for CSS entry points

Why:

Webpack 4 will soon have the ability to handle CSS inputs/outputs natively, but doesn't yet. As a result, when we add our CSS or Sass files as entry points and use the extract text webpack plugin, or the new webpack 4 compatible mini css extract plugin, we'll get bogus, extraneous JS files generated for each of our CSS assets. See [this issue](webpack-contrib/extract-text-webpack-plugin#518) for more details.

This change addresses the need by:

Using the `rimraf` package to remove the unnecessary files after build.

package.json

@@ -22,6 +22,7 @@
     "npm-run-all": "^4.1.1",
     "postcss-loader": "^2.0.6",
     "reset-css": "^3.0.0",
+    "rimraf": "^2.6.2",
     "sass-loader": "^6.0.6",
     "style-loader": "^0.20.3",
     "stylelint": "^9.1.3",
@@ -37,9 +38,10 @@
     "jquery": "^3.2.1"
   },
   "scripts": {
+    "clean-extra": "rimraf distribution/scripts/ie.js distribution/scripts/print.js distribution/scripts/styles.js",
     "lint:scss": "stylelint 'source/**/*.scss' --syntax scss --config stylelint.config.js",
     "compile": "webpack",
-    "build": "run-s lint:scss compile",
+    "build": "run-s lint:scss compile clean-extra",
     "start": "webpack --watch"
   }
 }