WIP: add pandas.hdfstore suppport


includes some other commits to make testing clean
- https://github.com/jreback/into/commit/82a6546ee5c6465a851601873f00ff05109a3c0c is in another PR already
- https://github.com/jreback/into/commit/836d5caaf2e3189882a53df343a18a785672c3a2 should be cherry-picked

- need to solve the resource disambiguation issue

  'foo.h5' -> PyTables
  'foo.hdf5' -> h5py

  but these should be dynamically determinable via the inherent meta data in the file
My preference here is to have tests that can be run with either nose or pytest.  I usually use context managers rather than fixtures for this sort of thing.  They achieve the same effect with IMO, marginal additional cost.