py-h5py: update to 2.8.0

Features
- allow registration of new drivers
- add option to track object creation order

Bug fixes
- allow slices with stop < start as empty
- improve building with custom hdf5 installation
- ensure libver defaults to LIBVER_EARLIEST
- improve handling of float types
- support non-ascii external paths on py2
- avoid crashing IPython auto-completer

API changes
- deprecate ``h5t.available_ftypes``.  This is no longer
  used internally and will be removed in the future.  There is
  no replacement public API.
- Do not sort fields in compound types.  This is account for changes
  in numpy 1.14.
- Minimum version of cython is now 0.23

(markd)