Allow addition in Hashes

Allows you to do x = { :a => 1 } y = { :b => 2 } # x + y => { :a => 1, :b => 2 }, but x and y are untouched # x + { :c => 3 } => { :a => 1, :c => 3 }

class Hash
  def +(add)
    temp = {}
    add.each{|k,v| temp[k] = v}
    self.each{|k,v| temp[k] = v}
    temp
  end
end