Support Multiple Auto Scaling Groups

[jbritten]

Allow multiple "autoscale" declarations.

I, too, manage two different production autoscale groups -- one for the app servers and one for the background job worker servers.

This change now stores an array of autoscaling groups, which will be iterated through as part of the elbas:deploy task.

Fixes #41.

[lserman]

edit: nvm. :)