Adding the ability to feed or override config vars form the environment

I think this should become:

``` javascript
if (envPrefix) {
  if (process && process.env && typeof process.env !== String)
  {
     _.merge(this.config, getConfigFromEnv(envPrefix));
  } else {
    console.warn("HEY HEY HEY, this feature is supposed to be used in node only :)")
  }
    
}
```