add raw h5py file with into, discover, ...

This will replace HDF5
remove HDF5 data descriptor
h5py: py3 compatibility
expr: fix split signature on selection, like, ...
Merge branch 'master' into replace-HDF5

Conflicts:
	blaze/__init__.py
	blaze/api/into.py
	blaze/data/__init__.py
	blaze/data/tests/test_interactions.py
	blaze/tests/test_resource.py
Merge pull request #867 from mrocklin/replace-HDF5

Replace HDF5 with h5py.Dataset