0.0.30 release

 - Vouchers
 - 2FA and mnemonic verification warnings
 - Rebranded from GreenAddress.it to GreenAddress
 - Made two factor obligatory in signup
 - Merged transactions with balance
 - Double spending detection
 - Safer external/social transaction URLs (private key in # hash part, not sent
   to server anymore)
 - Disallowed external transactions below 0.1543mBTC to make sure enough money
   is available for anti-dust rules and redemption fee
 - Modal dialog for redeeming external transactions from transaction list
 - display correct number of decimal places when converting currency to BTC/mBTC/uBTC
 - Fixed mnemonic encryption in signup
 - Fixed fiat values when paying bitcoin: URIs
 - other minor improvements