Add command line interface for juice

WIth less them 30 lines and just visionmedia/commander.js as dependencie we have a CLI for juice.

If you want to document in readme.md:
```
[sudo] npm install -g juice 
```

```
  Usage: juice -f path/to/file -o path/to/ouput

  Options:

    -h, --help           output usage information
    -V, --version        output the version number
    -f, --file [path]    File to be rendered
    -o, --output [path]  Name of rendered file
```