usability improvements and bugfixes in awsbox

it's sexy.  look:

    A tool to deploy NodeJS systems on Amazon's EC2
    Usage: awsbox.js <destroy|test|findbyip|zones|create|createami|list|update|describe|listkeys|addkey|removekey> [args]
    
      addkey:	add an ssh key to an instance: <instance> <file_or_dir>
      create:	create an EC2 instance, -h for help
      createami:	create an ami from an EC2 instance - WILL DESTROY INSTANCE
      describe:	get information about an instance (by instance id, or name)
      destroy:	teardown a vm, git remote, and DNS
      findbyip:	find a hostname given an ip address (via zerigo, requires ZERIGO_DNS_KEY)
      list:		list all VMs on the aws account
      listkeys:	list ssh keys on an instance: <instance name/id>
      removekey:	remove a specific ssh key from an instance
      test:		check to see if we have AWS credential properly configured
      update:	git push to an instance
      zones:	list amazon availability zones