fix box download

On `vagrant up` there is an error, when downloading box:

```
    production: Downloading: https://cloud-images.ubuntu.com/vagrant/trusty/current/trusty-server-cloudimg-amd64-vagrant-disk1.box
An error occurred while downloading the remote file. The error
message, if any, is reproduced below. Please fix this error and tryagain.

The requested URL returned error: 404 Not Found
```

I recommend you to use Vagrant's cloud storage: https://vagrantcloud.com/discover/featured