message: add explicit derivation scheme
diff: @@ -57,11 +57,17 @@ pub struct Wallet {
  pub config: config::Config,
  pub selection_policy: tx::fee::SelectionPolicy,
  + pub derivation_scheme: hdwallet::DerivationScheme,
  }
  impl Wallet {
  pub fn new(cached_root_key: hdwallet::XPrv, config: config::Config, policy: tx::fee::SelectionPolicy) -> Self {
  - Wallet { cached_root_key: cached_root_key, config: config, selection_policy: policy }
  + Wallet {
  + cached_root_key: cached_root_key,
  + config: config,
  + selection_policy: policy,
  + derivation_scheme: hdwallet::DerivationScheme::V2,
  + }
  }
  /// create a new wallet from the given seed
  @@ -73,7 +79,8 @@ impl Wallet {
  Wallet {
  cached_root_key: key.derive(BIP44_PURPOSE).derive(BIP44_COIN_TYPE),
  config: config::Config::default(),
  - selection_policy: tx::fee::SelectionPolicy::default()
  + selection_policy: tx::fee::SelectionPolicy::default(),
  + derivation_scheme: hdwallet::DerivationScheme::V2
  }
  }
  @@ -212,7 +219,8 @@ mod test {
  \"config\": {
  \"protocol_magic\": 633343913
  },
  - \"selection_policy\": \"FirstMatchFirst\"
  + \"selection_policy\": \"FirstMatchFirst\",
  + \"derivation_scheme\": \"V2\"
  }
  ";
  