refactor(@angular/cli): remove compression plugin

Followup from angular#4618

Author: filipesilva

package.json

@@ -103,7 +103,6 @@
     "webpack": "~2.2.0",
     "webpack-dev-server": "~2.2.0",
     "webpack-merge": "^2.4.0",
-    "webpack-sources": "^0.1.3",
     "zone.js": "^0.7.2"
   },
   "ember-addon": {

packages/@angular/cli/lib/webpack/compression-plugin.ts

@@ -4,7 +4,6 @@ import * as fs from 'fs';
 import { stripIndent } from 'common-tags';
 import { StaticAssetPlugin } from '../../plugins/static-asset';
 import { GlobCopyWebpackPlugin } from '../../plugins/glob-copy-webpack-plugin';
-import { CompressionPlugin } from '../../lib/webpack/compression-plugin';
 import { WebpackConfigOptions } from '../webpack-config';
 
 
@@ -75,12 +74,6 @@ export const getProdConfig = function (wco: WebpackConfigOptions) {
         mangle: { screw_ie8: true },
         compress: { screw_ie8: true, warnings: buildOptions.verbose },
         sourceMap: buildOptions.sourcemap
-      }),
-      new CompressionPlugin({
-        asset: '[path].gz[query]',
-        algorithm: 'gzip',
-        test: /\.js$|\.html$|\.css$/,
-        threshold: 10240
       })
     ].concat(extraPlugins)
   };

packages/@angular/cli/models/webpack-configs/production.ts

@@ -84,7 +84,6 @@
     "webpack": "~2.2.0",
     "webpack-dev-server": "~2.2.0",
     "webpack-merge": "^2.4.0",
-    "webpack-sources": "^0.1.3",
     "zone.js": "^0.7.2"
   },
   "ember-addon": {