fix bug on checksum of mnemonic ref
fix bug on checksum of mnemonic ref

lontivero/NBitcoin,MetacoSA/NBitcoin,stratisproject/NStratis,HermanSchoenfeld/NBitcoin,you21979/NBitcoin,MetacoSA/NBitcoin,NicolasDorier/NBitcoin,bitcoinbrisbane/NBitcoin,dangershony/NStratis,thepunctuatedhorizon/BrickCoinAlpha.0.0.1