add dev mode, update readme

build/webpack.build.conf.js

@@ -0,0 +1,16 @@
+var webpack = require('webpack')
+var merge = require('webpack-merge')
+var baseConfig = require('./webpack.base.conf')
+var path = require('path')
+
+var projectRoot = path.resolve(__dirname, '../')
+
+module.exports = merge(baseConfig, {
+  entry: './src/index.js',
+  output: {
+    path: path.resolve(projectRoot, 'dist'),
+    filename: 'vue-tree-list.min.js',
+    library: 'VueTreeList',
+    libraryTarget: 'umd'
+  }
+})