Machine must stopped state before they're destroyed.

https://us-west-1.api.joyentcloud.com/docs#DeleteMachine
add confirmation support to `vagrant destroy`
use keyname/keyfile for all authentication

Based on a few conversations at #ChefConf and the itchiness of my beard
we should just act as if password auth does not exist! =)
fall back to machine name if `node_name` not set by user

This follows the patterns of other Vagrant cloud providers like 
`vagrant-rackspace` and `vagrant-aws`.
display `joyant_keyname` when instance is created

This makes more sense then the ssh username and follows the pattern of
other Vagrant cloud providers like `vagrant-aws`.
fix trailing white space! >_<
Merge pull request #1 from schisamo/improvements

Improvements