fixed ReferenceError

```
ReferenceError: localStorage is not defined
    at localStore.set (/Users/XiNGRZ/Development/pm2.5/node_modules/min/min.js:211:9)
    at Object.min.set (/Users/XiNGRZ/Development/pm2.5/node_modules/min/min.js:1136:15)
    at /Users/XiNGRZ/Development/pm2.5/node_modules/min/min.js:1905:14
    at /Users/XiNGRZ/Development/pm2.5/node_modules/min/min.js:705:11
    at Object.min.get (/Users/XiNGRZ/Development/pm2.5/node_modules/min/min.js:1509:9)
    at Object.min.exists (/Users/XiNGRZ/Development/pm2.5/node_modules/min/min.js:702:12)
    at Object.min.hset (/Users/XiNGRZ/Development/pm2.5/node_modules/min/min.js:1872:10)
    at loop (/Users/XiNGRZ/Development/pm2.5/node_modules/min/min.js:1982:14)
    at Object.min.hmset (/Users/XiNGRZ/Development/pm2.5/node_modules/min/min.js:1996:7)
    at Strategy._verify (/Users/XiNGRZ/Development/pm2.5/app.js:34:7)
```

估计是 node v0.10.24 中对 undefined 的处理更加严格了？

总之还是严谨一点好……