fix CONFIG_FILE ReferenceError

CONFIG_FILE should be at the top level and not inside var config = (function...

Otherwise we get:

```javascript
ReferenceError: CONFIG_FILE is not defined
    at tunnelAction (/Users/leetreveil/Dropbox/browserstack-cli/bin/cli.js:380:95)
    at Object.runAction [as _onTimeout] (/Users/leetreveil/Dropbox/browserstack-cli/bin/cli.js:455:10)
    at Timer.list.ontimeout (timers.js:101:19)
```