Update dev dependencies (#3401)

- Everything still works as expected.
  - Remove bundlesize
    - It still uses libtorb which is deprecated and broken on Win and
      requires a full suite of build tools on Mac. Keeping it in the
      package makes it difficult for anyone filing issues to run tests.
    - See: #3396
  - Update grunt and it's plugins
  - Update karma to v4...so much faster!
    - Changed the karma config. Better changes: #3394
  - Update Webpack
    - Uses terser over uglify
  - Update eslint
    - Caused an error in util.js from the `global` directive so the
      directive is removed (it was not needed).
  - Update typescript
    - The old version of tsc didn't know about new features in
      @types/node (like `asserts value`).

Co-authored-by: Jay <jasonsaayman@gmail.com>

webpack.config.js

@@ -1,12 +1,13 @@
+const TerserPlugin = require('terser-webpack-plugin');
 var webpack = require('webpack');
 var config = {};
 
 function generateConfig(name) {
-  var uglify = name.indexOf('min') > -1;
+  var compress = name.indexOf('min') > -1;
   var config = {
     entry: './index.js',
     output: {
-      path: 'dist/',
+      path: __dirname + '/dist/',
       filename: name + '.js',
       sourceMapFilename: name + '.map',
       library: 'axios',
@@ -15,25 +16,9 @@ function generateConfig(name) {
     node: {
       process: false
     },
-    devtool: 'source-map'
+    devtool: 'source-map',
+    mode: compress ? 'production' : 'development'
   };
-
-  config.plugins = [
-    new webpack.DefinePlugin({
-      'process.env.NODE_ENV': JSON.stringify(process.env.NODE_ENV)
-    })
-  ];
-
-  if (uglify) {
-    config.plugins.push(
-      new webpack.optimize.UglifyJsPlugin({
-        compressor: {
-          warnings: false
-        }
-      })
-    );
-  }
-
   return config;
 }