REF: avoid returning self in io.pytables
Another small step towards making these less stateful
@jreback it looks like the LegacyFixed methods are not covered in the tests.  Any chance we can rip out those classes? also read_sparse_intindex, write_sparse_intindex, read_block_index, write_block_index, so we might not need BlockIndex/IntIndex (which are imported from arrays.sparse)? so i think i can blow away all Legacy stuff

i think these read the legacy_hdf dir in data/

but these are quite old iirc


also exception on line 635 can remove that is some versions prior to what we support now great, i'll make a PR specific to ripping that stuff out.  hopefully that will snowball into more simplfications thanks