Fix Sequence zero issue

[Wally]

Hi bro,

please help change file wallet.py line 43 to:
self._sequence = account['sequence'] if 'sequence' in account else 0 from "initialise_wallet" function

due to https://community.binance.org/t/why-some-account-dont-have-sequence/2663

seems like newly created wallet don't have "sequence", we have to handle it in SDK.

After you changed the code, could you please help release a new version on Pypi?

Thanks in advance :)