transaction_hash values should be hex, not base58

[automatthew]

Offending code is at least here

• https://github.com/BitVault/bitvault-rb/blob/master/lib/bitvault/bitcoin/transaction.rb#L179
• https://github.com/BitVault/bitvault-rb/blob/master/lib/bitvault/bitcoin/output.rb#L23-L29