BIP 32: Test vectors for leading zeros

These additional test vectors will ensure all future implementations are compliant with bip32. See https://github.com/iancoleman/bip39/issues/58 and https://github.com/bitpay/bitcore-lib/issues/47 Possibly these test vectors may be useful also: [bitcoinjs-lib test for this issue](https://github.com/bitcoinjs/bitcoinjs-lib/blob/4b4f32ffacb1b6e269ac3f16d68dba803c564c16/test/fixtures/hdnode.json#L180) [bitcore-lib test for this issue (pending merge)](https://github.com/bitpay/bitcore-lib/pull/9

Specification