def add_dependency(uri)
      self.config = hash_reassoc(config, :dependencies) do |set|
        set + Set.new([uri])
      end
    end
def add_dependency(uri)
      self.config = hash_reassoc(config, :dependencies) do |set|
        set + Set.new([uri])
      end
    end
Public: Add environmental dependency inheirted by all assets.

 uri - String dependency URI

 Returns nothing.