0.10dev-8f143b8

- Refactor MarginalTable and ConditionalTable into just Table
- Updated basic IPython notebook accordingly
- Added appropriate blocks on Table methods to execute on if the
  appropriate table type (most methods only work for marginal tables)
  - Added number system support that allows user to specify whether they
    want to use float, Decimal, SymPy integer, or SymPy float
    - Added a simple SymPy IPython notebook