Refactor: Don't include package.json into dist files

Instead of including package.json file into the build files.
Use webpacks DefinePlugin to define a global lib version.

build/webpack.base.conf.js

@@ -1,8 +1,10 @@
 'use strict'
+const webpack = require('webpack')
 const path = require('path')
 const utils = require('./utils')
 const config = require('../config')
 const vueLoaderConfig = require('./vue-loader.conf')
+const npmCfg = require('../package.json')
 
 function resolve (dir) {
   return path.join(__dirname, '..', dir)
@@ -72,5 +74,10 @@ module.exports = {
         }
       }
     ]
-  }
+  },
+  plugins: [
+    new webpack.DefinePlugin({
+      LIB_VERSION: JSON.stringify(npmCfg.version)
+    })
+  ]
 }