Fixed loading default country ranking bug

- Fixed default country ranking loading bug
- Grunt will now automatically load any `npm` lib which starts with `grunt-`
- Updated the `README` file with the missing `grunt install` command
- Added a library (`time-grunt`) to display grunt tasks performance

```
Execution Time (2013-12-20 22:30:22 UTC)
loading tasks  541ms  ▇▇ 1%
karma:unit        2s  ▇▇▇▇▇▇▇▇▇ 6%
karma:midway      2s  ▇▇▇▇▇▇ 4%
karma:e2e        35s  ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 88%
Total 40s
```