def http_headers
      req_headers = self.reject {|k,v| !k.start_with? "HTTP_" }
      normalized = req_headers.map do |key, value|
        new_key = key.sub("HTTP_",'').split('_').map(&:capitalize).join('-')
        [new_key, value]
      end
      Hash[normalized]
    end
def http_headers
      req_headers = self.reject {|k,v| !k.start_with? "HTTP_" }
      normalized = req_headers.map do |key, value|
        new_key = key.sub("HTTP_",'').split('_').map(&:capitalize).join('-')
        [new_key, value]
      end
      Hash[normalized]
    end
Extracts HTTP_ headers from rack environment.

 Example

   env = Client::Environment.new({"HTTP_X_CUSTOM" => "custom"})
   env.http_headers  # => {"X-Custom" => "custom"}

 Returns Hash with normalized http headers.