remove test dep

Author: Baitu Huang

.travis.yml

@@ -7,6 +7,6 @@ node_js:
 env:
     - TEST=true
 install:
-    - npm install
+    - cd test && npm install && cd .. && npm install
 script:
     - npm test

lib/plugin.js

@@ -1,4 +1,3 @@
-const webpack = require('webpack')
 const assert = require('assert')
 
 const {
@@ -126,6 +125,7 @@ module.exports = class VueFlagsWebpackPlugin {
     })
 
     // apply flag variable plugin
+    const webpack = require('webpack')
     const constPlugin = this.pluginOptions.watch ? new webpack.ProvidePlugin({
       [this.pluginOptions.namespace]: RESOLVED_FLAGS_PATH
     }) : new webpack.DefinePlugin({