Change seedlist creation to conform to NUTCH-2090

[sujen1412]

The Seed API was refactored according to https://issues.apache.org/jira/browse/NUTCH-2090.
The python code needs to be refactored to match the specifications of the new API.
Or we need backward compatibility in Nutch for the Seed API.

[sujen1412]

Work ongoing for backward compatibility - https://issues.apache.org/jira/browse/NUTCH-2246

[chrismattmann]

handled in #18

[chrismattmann]

@sujen1412 please review