Should refactor Blimpy::Box to support different "cloud" providers

[rtyler]

I can see it making sense to have something like this in your Blimpfile:

Blimpy.fleet do |f|
  f.add do |s|
    s.cloud :aws
    s.name 'amazon'
  end
  f.add do |s|
    s.cloud :openstack
    s.name 'private'
  end
end

[rtyler]

Starting work on this now.

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[rtyler]

There's a lot of things that need to go into this; major refactor of the Box interactions :(

[rtyler]

I think this can be mostly considered done as of 0.3.0.

Currently there aren't any other cloud boxes fully defined though.

[rtyler]

This work is complete.

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