add into(DataFrame, pytables Table)

An addition to `into` so that one can go directly from a pytables Table to a pandas DataFrame.

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Yeah, better ways to organize all of this would be welcome too.  For a while I was trying to keep `into` in different small files associated to the more complex of the two sides.  This breaks down pretty quickly though.  The two approaches that seem sensible to me are to have `n^2` `test_foo.py` files or to have 1 `test_all.py` file with `n^2` tests.