README PyPi Type-o

[brad-anton]

The README and PyPi page make reference sha3_228(), this looks like a type-o, should be sha3_224()

>>> import hashlib
>>> import sha3
>>> s = hashlib.sha3_228()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'sha3_228'
>>> s = hashlib.sha3_224()

[tiran]

Thanks, the problem has been addressed by PR #9.