Migrate from Browserify to Webpack (#372)

* Migrate from Browserify to Webpack

close https://github.com/zenorocha/clipboard.js/issues/371

 Author:    Guillaume Vincent <guillaume@oslab.fr>

* remove browserify and associated modules and update tests

webpack.config.js

@@ -0,0 +1,32 @@
+var path = require('path');
+var webpack = require('webpack');
+
+var production = process.env.NODE_ENV === 'production' || false;
+
+module.exports = {
+    entry: './src/clipboard.js',
+    output: {
+        filename: production ? 'clipboard.min.js' : 'clipboard.js',
+        path: path.resolve(__dirname, 'dist'),
+        library: 'Clipboard',
+        libraryTarget: 'umd'
+    },
+    module: {
+        rules: [
+            {test: /\.js$/, exclude: /node_modules/, loader: "babel-loader"}
+        ]
+    },
+    plugins: production ? [
+            new webpack.optimize.UglifyJsPlugin({
+                beautify: false,
+                mangle: {
+                    screw_ie8: true,
+                    keep_fnames: true
+                },
+                compress: {
+                    screw_ie8: true
+                },
+                comments: false
+            })
+        ] : []
+};