Cleaned up rakefile
        - can get rid of mkdirs
Collect bill_id
        - We need to record the bill_id to match up votes and text
Rationalized data preparation

    - Separated creation of data files into separate python scripts,
      starting with prepare.
    - We need raw counts, not the tf-idf scores. We would like to use
      tf-idf to reduce the size of the vocabulary; I'll raise an issue.
    - Expanded criteria to download text for house resolutions as well as
      they are voted on in the Senate.