updated alpha-README instructions to include adding RPC username/pass…

[metacoin]

I was getting the following python error when running $ ./contrib/sidechain-manipulation.py:

$ ./contrib/sidechain-manipulation.py generate-one-of-one-multisig sidechain-wallet
Traceback (most recent call last):
  File "./contrib/sidechain-manipulation.py", line 95, in <module>
    address = sidechain.getnewaddress()
  File "/home/ubuntu/elements/elements/contrib/../../python-bitcoinrpc/bitcoinrpc/authproxy.py", line 136, in __call__
    response = self._get_response()
  File "/home/ubuntu/elements/elements/contrib/../../python-bitcoinrpc/bitcoinrpc/authproxy.py", line 182, in _get_response
    response = json.loads(responsedata, parse_float=decimal.Decimal)
  File "/usr/lib/python2.7/json/__init__.py", line 351, in loads
    return cls(encoding=encoding, **kw).decode(s)
  File "/usr/lib/python2.7/json/decoder.py", line 366, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python2.7/json/decoder.py", line 384, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded

To fix this error I had to edit sidechain-manipulation.py to include my rpc username and password. It wasn't clear from the README this was a necessary step.

[TheBlueMatt]

Can you also update the pointers in the next section? It now says 1-4, should say 1-5, I think.

[metacoin]

I've updated numbering in subsequent sections to match the numbering I changed in my first commit.

[sipa]

ACK