Make the module hashlib-compliant

[varunkumar]

mmh3 is currently not hashlib-compliant. This makes it challenging to use it as a replacement for md5 or other cryptographic hashes. A wrapper can be built to make this module hashlib-compliant. One should be able to use the module as hashlib.md5.

update() -- update the current digest with an additional string digest() -- return the current digest value hexdigest() -- return the current digest as a string of hexadecimal digits intdigest() -- return the current digest as an integer copy() -- return a copy of the current mmh3 object reset() -- reset state