def with_headers(new_headers)
      unless new_headers.is_a?(Hash)
        raise ArgumentError, "New Headers should Hash object."
      end

      headers.merge!(new_headers)
      self
    end
def with_headers(new_headers)
      unless new_headers.is_a?(Hash)
        raise ArgumentError, "New Headers should Hash object."
      end

      headers.merge!(new_headers)
      self
    end
Public: A fluent way to add HTTP headers.
 Headers informed here are merged with headers attribute.

 new_headers - Hash with headers.

 Examples

   entry_point = Restfolia.at("http://fake.com")
   entry_point.with_headers("X-Custom1" => "value",
                            "X-Custom2" => "value2").get

 Returns self, always!
 Raises ArgumentError unless new_headers is a Hash.