Config::set($key, $val = '')

$key string or array if $key use . connection, it will be considered as get value from multi-dimensional arrays by index. For example:
```
Config::set('test.foo'); // look like $config['test']['foo'];
```
if $key is array it will be merged
Config::get($key)

$key string support use . connector to search multi-dimensional arrays. For example: Config::get('test.foo')
load configure file from path Config::load($path, $defaul = 'default.php')
```
Config::load('./config/develop.php');
```

support auto load by command line arguments

    // set path
    Config::load('./config');
    // run script
    php demo.php --env staging