naga viper latest claimant world's-hottest-pepper title beating predecessor bhoot jolokia scoville units tongue-scorching chili hotness researchers warwick university testing naga viper found measures scoville scale rates heat tracking presence chemical compound comparison varieties jalape peppers measure range bhoot jolokia scored scoville units naga viper produce nagaland pepper creation gerald fowler british chili farmer owner crossed hottest peppers including bhoot jolokia 