def variation(id)
      @url = "variations/#{id}"
      raise OptimizelyError::NoVariationID, "A Variation ID is required to retrieve the variation." if id.nil?

      response = self.get(@url)
      Variation.new(response)
    end
def variation(id)
      @url = "variations/#{id}"
      raise OptimizelyError::NoVariationID, "A Variation ID is required to retrieve the variation." if id.nil?

      response = self.get(@url)
      Variation.new(response)
    end
Returns the details for a specific variation.

 == Usage
  optimizely = Optimizely.new({ api_token: 'oauth2_token' })
  variation = optimizely.variation(12345) # Look up the variation.