Merge pull request cuixiaorui#51 from bigfatDone/master

添加dev模式下监听源文件是否有改动，如果有改动，重新打包。

Author: cuixiaorui

package.json

@@ -5,6 +5,7 @@
   "main": "lib/mini-vue.cjs.js",
   "module": "lib/mini-vue.esm.js",
   "scripts": {
+    "dev": "rollup -c -w",
     "build": "rollup -c",
     "build:type": "tsc -p ./tsconfig.type.json",
     "test": "jest --no-cache"