"Current" deploy directory for export

Hey. I'm using this script to deploy an application that uses sidekiq onto Ubuntu 14.04 (so that means by default I get Upstart, for better or for worse :wink:). Upon invoking `foreman:export`, I end up with an upstart script that ends in:

```
exec su - rails-assets -c 'cd /home/my-app-user/rails-apps/my-app/releases/20160311190512; # ...
```

On the README, in the USAGE section, it seems like you're suggesting that exporting the Procfile like this is a one time deal and need not be done on every deployment. Is that right? I did this, and of course it worked and I didn't actually examine the Upstart script which was generated. But then after 5 deploys, my sidekiq stopped existing :boom: :exclamation:

Personally, at the least, I think this should have clearer documentation (which of course I will be happy to add). But also, do you think that maybe by default having it export the `current` (symlinked) path would be more intuitive?