WIP: Add support for Capistrano 3.0.

This takes care of #1 too. 

This is the initial cut for Capistrano 3.0 support. I followed many of the recipes provided by default in the new Capistrano versions. You should be able to just add this into your Capfile:

```
require 'capistrano/puma`
```

I am still running some tests locally to make sure it works in all cases. Let me know if you find anything!